I had the BGE Emerald 4000 on my first motor home (a 27ft Georgie Boy). Mine was very noisy. The muffler was old and rusty, so I replaced it. Didn't help. I put my hand over the end of the muffler tailpipe and I found that the connection between the exhaust manifold pipe and the exhaust pipe that connects to the muffler had come loose. You have to take the muffler off to get to the flange bolts. I did this, tightened them, but in due time they came loose and the bolts and gasket fell out. I bought a new gasket and hardened bolts with jamb nuts. Fixed the problem, never came loose again. To see this part, go to Cummins Onan and look at the exploded view in the parts manual.
