Back to what I said earlier about where the sound is coming from. It actually seems to be coming from under the car from where the cat is. When accelerating sometimes I can even feel a vibration under my feet. I checked to make sure everything was tight where the header attaches to the engine and where the header attaches to the cat. I think I may have forgotton to mention earlier that the header did not line up perfectly with the cat but the donut seems to close off the gap pretty well. does anyone know what could be done to stop the noise?

 

my suggestion to you (that was given to me for my similar problem) is that you take a piece of rubber hose or garden hose and move it along the installed parts with an ear to (but not directly on) the other end. chances are excellent that you will be able to locate the source of the leakage. also...try to retighten those bolts, they do tend to slip a bit while breaking in your metal.

check the manifold as well. make sure to run that hose all along the connection welds and the bolt plates, especially near the catylitic converter. it is possible that you have misaligned the gaskets or donut ring regardless of the care taken in getting it right. professionals regularly need to make adjustments after new installation.

if the welds even have a small crack in them, it is possible that with the extra heat and pressure from the revved exhaust that there could be enough of an expansion to create a small leak. also, the pipes not lining up correctly could be caused by a warped header. be sure it's to factory spec. the likelihood of having a warped part rises exponentially with the reduction of the price paid (in other words, beware of ebay headers).

also, if the rest of your exhaust is really old, misaligned, or otherwise flawed, it could be resonating rather strangely. this is particularly true of catylitic converters. if it has been damaged by exposure to excess unburnt fuel (by means of an O2 sensor failure combined with continued driving), it could produce strange resonations. my guess for you, not having seen it, is that the misalignment has caused your exhaust to vibrate more on it's hangers. that misalignment is probably also culpable for your apparent leak.

good luck, let us know what you find.

 

thanks guy. I really appreciate your in depth response. I guess I'm just going to take off the header from the cat and try to align it better. Thanks for all the help!

 

no problem. that's my project as well when I get back to school. that and saving up for an RS-R ex mag cat back system, a magnaflow cat, and some decent headers.

good luck, and ask questions if you got em.