I ran straight exhaust (no cats/no muffler) to my rear bumper. The 2.9 ran like a scalded dog & sounded like a dirt track car, but I lost 5 m.p.g. & couldn't stand near the back of the truck because it started running so rich!
So I put the cats back on & ran dual exhausts from the cats tail to the back bumpers--got my 5mpg back plus some & it sounds almost like a v-8! SO, I cut 20" off each tail-pipe and installed ------ -------- mufflers & now it sounds just like an ancient 289 v-8!!!