Cat Recommendation? - Pontiac G8 Forum: G8 Forums -
Exhaust Tech Headers, Catbacks, Mufflers, lack of mufflers

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post #1 of 6 (permalink) Old 11-05-2016, 10:56 PM Thread Starter
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Unhappy Cat Recommendation?

Hi All,

09 GT with SLP long tube headers. Last year I had a rattling sound under moderate to high throttle. Turned out to be the catalytic converter monoliths were disintegrating. I bought replacement catalytic converters and installed a Borla catback system, and got a tune as SLP recommended (they said the cats disintegrated because of the lack of a tune, "running rich"). I ended up getting a tune from PatG, and everything has been great- as all say, it really woke the car up!

The issue is, the rattling sound is starting again, less than 11 months later. PatG says everything looks good with the tune, so I'm pretty certain it's due to a problem with the SLP cats. I would like to replace them with something other than the SLP cats. Does anyone else have SLP long tube headers with non-SLP cats? Anyone else have this rattling issue? If so, what did you use? It seems most of the cats available are like the OEM cats and have a bent pipe as part of their design... the SLP cats are just straight and clamp on. I'd like to replace these and get back to enjoying the car!

Going cat-less is not an option for me.


P.S. If anyone has the dimensions of the SLP cats, that would be useful as well! (No lift/ jacks, so measuring would be difficult).
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post #2 of 6 (permalink) Old 11-09-2016, 12:07 AM Thread Starter
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Bump... any advice folks? Thanks in advance!
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post #3 of 6 (permalink) Old 11-09-2016, 08:05 AM
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Solo cats? Kooks cats? Just trying to help since nobody else is chiming in. My years old Kooks have done great.

RotoFab intake, Kooks mids, Solo Axle-Backs
Patrick G tuned to the note of 419whp / 416tq
VMR710FF 19x9.5 all around.
Brembo rears

Gone- 2009 MGM GT
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post #4 of 6 (permalink) Old 11-09-2016, 11:25 AM
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I have the same issue. Exact same set up. WI'll slp Warranty them?
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post #5 of 6 (permalink) Old 11-09-2016, 09:08 PM
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When you say you can't go cat-less, do you mean you need the functionality of the catalytic converter?
If you need the function than try switching to kooks. I hear theirs hold up a little better.

If you just want a Simple fix, remove the honeycomb from the slp cats and be done with it.

2008 GT/G8: first 888
MagnaFlow full exhaust with free flowing cats
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post #6 of 6 (permalink) Old 11-09-2016, 10:19 PM Thread Starter
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Thanks for the replies!

jerminator: Thanks- looked into Kooks and they are ~$1k and don't seem like they will fit without some cutting.

2oo9g8gt: Glad to know I'm not alone. No, last time they said the tune (or lack there of at the time) was to blame. They said their cats carry a 90 day warranty.

ZIm: Yes, for smell and environmental reasons I don't want to go catless (it's my daily). But yes, it seems like the options are american racing headers metallic cats/kooks, or to gut them... Brought it to the dealer today and they said everything checks out as far as they can tell and said to just keep an eye on it... guess we'll see. More time to save for the better stuff I suppose.
P.S.: Finally got the wheels mounted today, by the way- can't wait to see them in daylight!
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