I need a replacement for the muffler for my 1983 Onan 3.0 RV - input is on the top, exit is out the back - it's a round cannister, perhaps 6" diameter. Is there something significant about an Onan brand muffler, or can I get same or better noise reduction replacing the in-the-top out-the-back style muffler with a 90 degree elbow and a conventional or tractor muffler ? Has anybody had any luck, good or bad, with this type of substitution ? Thanks for any help.