I've had the same set on two cars now. When I had them on my old Duster I used a "H" pipe. When they went on the 'Cuda I went with a "X". Both cars had very similar engines and TTI headers. The only difference was between "H" and "X" was the fact that the Duster had 2 1/4 tailpipes and the 'Cuda is 2 1/2 all the way through. No resonance with either setup. Personally I prefer the sound of the "X". Both engines made good torque, they had different transmissions [ 727 vs 5 speed manual ] and a few other differences so it's a little difficult to make an "apples to apples" comparison as to which "X" vs "H" gave the best performance. Both cars are fairly loud, but not so bad that you can't hear the radio or carry on a normal conversation. I wouldn't hesitate to buy another set.