My exhaust goes from a 3"vband off the turbo (Garrett Gt4088) to 4" turbo back with a HOGG performance augmentor muffler.
...it's a diesel truck performance muffler that was the quietest that the company made. Got it on ebay for like 40 bucks new.
I'll try to post a sound clip when I get the chance, but it's not any louder than my stock Dp/3" catless obx muffler combination.
The only thing is that the muffler is 8" around. It's huge and looks kinda goofy, but whatever, I'm not building a show car.
I did have to put a number of bends in the exhaust that the 3" didn't have to gain the most clearance. I have at least 4" of clearance under the lowest part of it (at the differential) and have NEVER scraped it on anything. Ever.