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Discussion Starter #1 (Edited)
Got the Maximizer 1&7/8" stainless longtube header with 3" x-pipe catback kit from ebay for $700 + $95 shipping. Rumor has it, they are rebranded OBX or something, but cannot confirm. I received them in about 6 days, and the packaging was very well done. It came with header gaskets, and axleback gaskets, but I bought new gaskets and new header bolts for both from GM because the supplied gaskets looked very cheap. It came with 8 spring bolts for the ball flanges. It did NOT include nuts for the axlebacks. The stock piping has internal threads for the axleback bolts, but the Maximizer pipes do not thread, so you will have to find some nuts to fit the stock bolts for the axlebacks.

I was very impressed with the quality. The welds, flanges, and bends were all smooth. Even the merge collector was smooth.

The install went SUPER easy, and I had it done in under 4 hours start to finish. I did not have to remove the spark plugs, but I did have to temporarily disconnect the steering shaft to fit the driver side header in. The passenger side slid smoothly in. There were no sharp edges at all. Everything bolted up smoothly. The measurements and dimensions all fit perfectly. Bottom line, it was a direct, perfect fit. The hardest part of this entire install, was removing my stock O2 sensors.

The resonators after the headers are actually real resonators, they are not just a hollow pipe. When you look inside, the inner walls have holes for baffling, but I couldn't tell what was in it. I plan to remove them and have some 3" Thunderbolt 300cell cats installed, and take some "muffler-delete" axlebacks that I have and install Hooker MaxFlow mufflers that I have here, and I will update this when I get those installed.









 

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Discussion Starter #2 (Edited)




I thought that this might hit the frame, but I have not had a single problem with it yet.






 

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Discussion Starter #3 (Edited)




Only flaw: This little metal flake hanging off the side of the collector merge. I just poked at it with a screwdriver and it fell off easily, and now it is smooth.




 

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Discussion Starter #4 (Edited)
And last but certainly not least, the sound clip. This is on a SuperChips 91 Octane Rotofab tune. I will have it dynotuned next week.

I'm pleased with the sound of the GXP mufflers. It is nice and calm cruising, and very tame inside the car. There is zero drone, rattle, or unnecessary noise. I am still installing Hooker MaxFlows soon though.

 

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Looks awesome, and your car is gorgeous also by the way! Love the wheels and brake upgrade….. Is that a catch can in the second to last picture?

You will be very happy with the increased flow (in volume and power), enjoy!
 

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Discussion Starter #6
Thanks! Yes, that's a catch can. It was essential when I saw how much oil was inside the intake manifold.

Can't wait for a REAL tune and my Hooker MaxFlows to go on!
 

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Looks and sounds great. Having a lift certainly helps things go a lilttle quicker :)
 

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Lucky! Mine did rub on the passenger side subframe, nothing a little grinding couldn't take care of.

Have you noticed if the the x-pipe moves if you push up/down on it? Mine would sag after a couple miles of driving, found that it kept pivoting at the rear ball flanges no matter how tight I had everything.

Mine is definitely quieter. I guess I need to "borrow?" your GXP axlebacks... lol
 

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Discussion Starter #10
The xpipe is not hanging down at all.. yet.. We considered that when installing, and tried to position the flanges to help with that. It's nice and tight.
 

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Installed mine yesterday and had the exact same experience. No rubbing, no fitment issues, and everything lined up perfectly the first time. I had to replace an o2 sensor that I rounded off. I tightened the band clamps that were provided as far as they would go and they still leak like crazy so those will be a welded up soon.
 

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sounds decent ! make sure and tighten the bolts after a couple heat cycles , and make sure the pipe doesnt drop down and hit the cross brace

also a couple spot welds arent a bad idea

still interested in the gxps
 

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Discussion Starter #13
Yeah, I'll tighten everything up again this week. So far, the mid-pipes have not drooped down at all.

I had the car at an exhaust ship to weld in my Thunderbolt cats in place of the resonators and weld up the two pipe connections that have the clamps. NO LEAKS! I'm going back another day soon to have some Hooker Maxflow custom axlebacks made up!
 

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Discussion Starter #16
did you need to use ox sensor extensions with this set up? thanks, nice post!!
Yes, on the driver side. Now that I think about it, I didn't even try to hook up the O2 without the extension, I just went ahead and hooked it up since everyone said they needed it. The driver side O2 connection is REALLY tucked up in there though, it would be a TIGHT fight if the stock wiring did manage to fit.
 

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thanks, yeah these look very good for the $$$!! you think stock GT muffler would be a lot quieter? oh, what brake set up do you have on your car?,thanks again.., matt
 

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Nice....just ordered a set. Where did you buy the O2 extension? Will be using GT axle backs for now. Should still be a considerable improvement in sound though without 4 cats, center muffler and bullet mufflers that choke the OEM exhaust. Oh, and how were your factory header gaskets? Should I get a set of them? I have 50K miles.
 

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you think stock GT muffler would be a lot quieter?
Much quieter, I wish mine sounded like Hollo's, even on cold start it doesn't get near his level of loudness. You can tell that I have an exhaust if you have heard it stock(you can definitely smell it, lol) but it is not much louder. On WOT it gets deep and sounds good, that's when it comes alive. I think the GXP mufflers make it sound perfect, I'm hoping Hollo would be nice enough to pass them down to me...
 

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Discussion Starter #20
thanks, yeah these look very good for the $$$!! you think stock GT muffler would be a lot quieter? oh, what brake set up do you have on your car?,thanks again.., matt
GT mufflers would definitely be quiet. Honestly, even the GXP mufflers were very tame driving around. Cold start and revs sound much louder in the video then they do in the car.

Nice....just ordered a set. Where did you buy the O2 extension? Will be using GT axle backs for now. Should still be a considerable improvement in sound though without 4 cats, center muffler and bullet mufflers that choke the OEM exhaust. Oh, and how were your factory header gaskets? Should I get a set of them? I have 50K miles.
I actually got the wrong type of O2 extension, made for an LS1 car, and I had to trim the plugs on both ends a bit, but they are sold on a lot of GM aftermarket websites. Go ahead and spend some pocket change and get new GM gaskets. Always a good idea when taking off exhaust manifolds. They are a crush gasket. Not saying they can't be used more than once, but I'd hate to do all that work to have a leak.

Much quieter, I wish mine sounded like Hollo's, even on cold start it doesn't get near his level of loudness. You can tell that I have an exhaust if you have heard it stock(you can definitely smell it, lol) but it is not much louder. On WOT it gets deep and sounds good, that's when it comes alive. I think the GXP mufflers make it sound perfect, I'm hoping Hollo would be nice enough to pass them down to me...
Already got the GXPs gone, and my Hooker MaxFlows in place. I like the Hookers sound much better! The cold start and revs on the Hookers are a hair quieter, but they are a hair louder cruising around... A much cleaner, refined tone. I'm still waiting on a good time to get an exhaust video!
 
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