I bought an "aftermarket dealer add on" dual exhaust system and installed it. Stock headers into H pipe, mufflers under the rear seats, and exhaust pipes over the rear axle and straight out the back ala GT style. The whole setup was aluminized steel, and is holding up great, but the mufflers are loud INSIDE the car. The sound out the back is not obnoxiously loud, but from 20 to 45 (around town) it's starting to drive me crazy. I've got the black rubber sound absorbing mats underneat the OEM replacement carpet with the Jute backing. Are the higher priced mufflers made of welded stainless really that much better at keeping INTERNAL resonances down? I understand that one brand has a "40" and a "50" style muffler, with the "50" being a bit quieter, without undue restriction. Can some of you guys tell me what you're using and give some kind of description of the sound? I'm looking for a "manly rumble" if that makes any sense to you guys. Right now I have that sound outside, but it's a little annoying INSIDE!! It quiets down OK at 55 and higher...

 

i have dual exhaust and flowmasters. sounds real good but the inside sound was a little loud, especially at 45 mph. i pulled the interior and seats in the back and put the silver insulating material under the carpet, seat and anywhere i could find from the trunk. it really helped. my wife even commented that it was quiter. my car is a convertible.

 

hmm i think you gotta get used to them i know i did in my truck

 

i went with the flowmaster knockoffs, flow sound and they aren't that loud, just turn the radio up man! really though you might want to double up on the sound deadener and even by some that isn't form fitting and make sure each and every inch is covered with the stuff. You'll of couse get noise through the doors as well if you don't insulate them, and like someone said above make sure the trunk is sealed too.

 

Not sure if you want to change the front H to an X-pipe, but when I switched to an x-pipe crossover, my exhaust tone was quietier in the same 25-45 range. Noticeable performance advantage too. Also I used dynamat (in addition to the stock rubber mat and carpet) towards the rear of the interior to help deaden that good ol flowmaster drone. that stuff works great.

 

It seems that 45 MPH is the magic Drone point for Flowmaster seriess 40s. Mine are rather annoying inside the car at that speed. My wife doesn't like riding in the 72 because of that. I think I am going to go with series 50's or Ravins when I re-do the exhaust.