I switched my muffler about 6 months ago from a "fart can" to a dynomax muffler. I asked the shop to add a resonator to my car (b/c I got a ticket for an inadequate silencer). Ever since that day, it has sounded like I had a header leak. I took it back to the same shop about 3 different times; they only made the leak sound worse. After the engine was warmed up or hot weather (we had triple-digit temps recently) the sound would nearly disappear; like the heat caused the metal to expand, closing a gap or something. However, I just recently changed my exhaust to a 2.25" customer cat-back, with a Thrush resonator. The sound is gone? I was thinking possibly that the first shop put a highly-restrictive resonator on my car that gases were leaking out the ball and socket joint where the header and the down-pipe meet? I was curious if someone has similar problems? Is it just the pacesetter header and the bolts that hold the joint together might need to be tightened on a regular basis? I'm glad the sound is gone, I was just hoping the lack of aftermarket engine mounts didn't possibly crack my header. Sorry for the long post, it's just something that baffles me. Thanks for your all's input.