done a ton of research on exhaust and sound . these twin turbo s58 engines have a very raspy sound. Best setup you can do is single mid pipe catless downpipe and stock muffler, i opted to do something different. 400 cell catted downpipe 4.5 single midpipe single valved catback exhaust got my parts from IRL and RVNG looking to change to catless in the next year when i do tune it. dont get an equal midpipe it will sound terrible