Bruce, my old car has a 2 1/2" Magnaflow that's not too bad unless you put your foot to the floor, but it can be a bit irritating at higher revs. We were running the new engine on a Stuska dyno with a piece of 90 degree bend 2 1/2" pipe about 18" long and the Dynomax was quieter than a Magnaflow. The Dynomax is smaller, too (not as long).