alright so this is the prob. when i rev my car in neutral it makes this wierd rattling noise. it only does it when the car is warm. it comes from the middle of the exhaust. blown gasket? or is it some thing. i have a high flow bonez. and a stock main cat. also with that wierd rattling noise theres a noise that sounds like hot exhaust gases coming out of a small hole. lol. suspecting that when they put on the high flow they didnt use new gaskets. or is it something else? thanks!

 

look under the car on the both sides by rear wheel, there is a suspension component that the exhaust can hit, mine does the same thing

 

have an s4 turbo? It could be the twin scroll not adjusted right.

 

I got a weird tapping noise too, its only at idle though. One night it was acting up real bad, i was cruising through a partking lot about to park so i put it in nuetral to slide into the space, when i did it started tapping real bad, then i put it in gear and applied gas and the tapping went away, let off the gas and it came back.

Stock exhaust, i think its my cat though because its in pretty crappy condition.

 

??? you can adjust the twin scroll? maybe thats why mine is working. how do you adjust it?

 

I got some rattling when the car warms up and if I rev it some. Although it can be heard when the idle is a little higher.

Its really annoying, I've been told it could be a loose heat shield. (I do get a lot of interior heat too.) I'd probably check for loose bolts and nuts too. Anyways, haven't had the chance to look under my car yet but will do so soon.

 

i have no heat shields and i got an s5 turbo. hmm what could it be? ill check that suspension thing.

 

Get under the car while it is running, find the noise.

 

If you overheated the cat a few times it will wreck the material that holds the core in place, and it will rattle like crazy.

 

While you're under the car with it at idle, have someone cover the exhaust tips(with rags), and listen/feel for escaping gases. When I say feel, I don't mean place you hand on the exhaust, but you can possibly feel the hot gas coming out gaskets, holes.

 

look under there @ the can. you'll notice the actuator arm has a nut on there as well as another odd piece. loosen the nut and take off the snap ring on the pin. That little arm should screw in and out. then tighten the nut up against it and it will keep it from moving. if your arm is loose in there it will make noise like mine does(or did... its not completely gone )