O.k., I have 70 cuda, 360 with edelbrock alum heads. roughly 9.5:1 compression.comp cams 280h 484 lift cam tti headers. tti x-pipe , flowmaster 40's, 2 1/2" tails thru the valance with factory cuda tips. I originally did the magna flow turbo mufflers but they were just too close to stock sound . I switched to the flows and although it sounds great in every aspect except idle. at a low idle it sounds like there is a flutter or like paper is hanging in front of the tips??? I don't know if the factory tips are the problem because of the crappy 1 7/8 pipe that just ends in an akward spot inside the rectangular tip.or if an x-pipe will sound this way by blending both banks of the engine? it sounds too weird to leave alone!!!! Anyone else experience this? by the way, everything mentioned is brand new!