Just installed a 6 X 18 inch round magnaflow muffler with 2 1/2 inch pipes with full tail pipe for now. Brand new but sounds good so far Just loud enough to hear with the radio off at hwy speeds. off throttle very quite. Sounds good revving but not that loud perfect for what I want. No drone. Waiting for the computer to adjust but definitely pulls much harder at 4000 rpm .
Years of working on race motors for cars and roadracing motorcycles I know that straight through mufflers make the most power but are loud, so I took a chance on running a magnaflow 18" round muffler. After hearing the Off Road Pro-Series (a 14" X 5" round) I really liked it but it seamed too loud, so I decided on the 18" X 6" round. Ovals reduce flow but are good to quiet down big motors. But with 4 cats on a V6 an oval seams over kill and I was right the 18" round keeps it tame while maintaining max flow... I'm also copying Bad Ass Mufflers who uses all round mufflers for his exhaust.