On both a single cam setup I had as well as a fully built turbo B I had a 2.5'' thermal in and out muffler (turbo muffler) and a 3'' for the B-series. They were both quiet and sounded great on full throttle. Here's a video of the Fully built B in my hatch, open dump though. I personally think straight pipe sounds the best in my opinion for boost but that is just me as I just love hearing the turbocharger tunes


Fully built turbo GSR with a .70 trim, 3 inch straight piping 3in/out thermal research turbo muffler with no cat or resonator and open dump.