What is it. how does it work.

Someone correct me if I'm wrong, but I think that they're just sticking a couple washers at a flanged exhaust connection. It creates a leak path that is unmuffled.

It isn't something that I'd do.

doesnt sound like a good idea. thanks for answering

It works though

Just noise or have people got power from it.

It's not unmuffled. There are a muffler and resonators in the exhaust well before the flange behind the axle. Yes, it creates a "leak", but it is far from unmuffled. Give it a shot if you are wondering. It doesn't sound at all like a leak. It actually sounds like a good OEM exhaust.

It's been compared to axle-back muffler systems.

I did it to my car on sunday, it sounds great. It cost me nothing since I had some spare washers in the garage.
You should try it, it will cost you less than $1 and less than 10 min to do, if you don't like it you can remove them later.
It will not cause any problems or issues to your car.

Thanks for the answers when I get home today I'll give it a shot. I'll let you guys know how it works out.

do it!

I separated the wheels and all are pending sale.

That's good to know, but...wrong thread! Ha!

I had it on, off, on a different way, and now back to stock. It really sounds decent. Something that would be fun to have on the weekends, and take it off for the commute. Check other threads for more info.