You may want to try some sort of straight through style muffler, like magnaflow or the dynomax ultrflow mufflers. I doubt you will see 50 hp from the muffler, maybe 5-10 if your lucky. IMHO, flowmasters sound better on larger displacement motors, I have one on my 4.0 explorer and it sounds good, but it sounds much better on V-8s and such.

Dan

92 Rodeo, 3.1 TB crank, custom bumpstop spacers, DOR shackles, Flipped ball joints, D44 Rear, 4.56s and new magnaflow cat and dynomax ultraflow muffler Since been replaced by a 2 door Explorer on 31's shackles, cranked torsion bars and full exhaust