I have a Force II on my Camaro. Nice rumble but mellow at idle and cruise speed. I drive about 60 miles a day to and from work, so this matters.

I once put a Hooker Aerochamber on a stock Chevy 3500 w/ a 350 when the original muffler crapped out. Sounded great, but there was a cab resonance from time to time. But I like the muffler so much I bought another one for an inline six I built up for a Ford.

 

Flowmaster Delta Flow mufflers are designed to cancel out those sounds.