I know this thread is years old, but I did want to let the crew know about a muffler and resonator that I installed on my van. Im heading out for a long Alaska road trip in a couple of months and really needed to quiet this van down. So, after some research, I found these guys:
They set me up with the parts which I had welded in place locally. we put the resonator located all the way in the rear as it turns to exit behind r-rear tire. What a difference. I have no idea about performance, but the quiet cab is so much more enjoyable. Specifically, these are the parts:
stl-35 (stealth muffler) 28" long and a qr300l resonator that is 22" long. Very reasonably priced, too.