Just thought I would add to this thread...
for the last 5 years I have had the TTI 2.5 inch exhaust kit on my Challenger, with the Dynomax turbo mufflers. always had a drone at cruising rpm, and sounded good on the outside but loud on the inside. if the ride was longer than 20 minutes, it was a guaranteed earache.
I tried putting on some glass packs behind the mufflers and they took off the idle and mellowed the rasp, but didnt do chit for the drone.
just got done putting on the ebody 6pack Accurrate system on to replace it, and wow what a difference. The system bolted right on (way easier than TTI), except for needing a couple of clearancing hammer hits (the driverside torsion bar and the passenger side fast ratio idler arm (which TTI needed too)) and the sound is perfect. Finally !
it still rumbles at idle, and it still has a noticeable performance sound at 3500+ rpm but there is no drone at cruise or inside the car while idleing. I can hear the engine and I can hear the radio.
maybe I lost 10 horsepower but I dont race so Ill never really notice it missing.
Accurate Exhaust has a sale going right now for 10% off.
the resonators are 2-1/4 diameter, as are the mufflers and the over-axle-pipes, but on the 6pack kit, the head pipes are 2.5 There is a place that you can slip in a H pipe too, so thats on my summer Welding list of "things to weld".
