I had my magnaflow cats welded into my O/R prochamber. I guess I can't call it an O/R prochamber any more. The cats are more like kittens. I surprised how small they are-much smaller than stock cats. The appear to be about 12" long and less than 10" in diameter. I think it sounds a little deeper, but maybe not as loud. It doesn't sound as raw. Overall I guess it cleaned up the sound. The best part is no exhaust fume smell.
guess i wouldn't have spent the money a mid muffler set up would fix up a raspy h or x pipe if that was the reason.. or maybe you have emissions there?? anyway just my .02
and i know i had a few with just straight pipes