[bestgenman]

Ralph,  unless I have missed something, there should be two pipes routing exhaust out from underneath.  I’m not sure which year coach you are working on so, I will tell you what is commonly the method of construction.  There are two sources of exhaust gasses, the generator, and the Aqua hot.  Depending on the year, the older coaches route those underneath and joining into one tube with a vertical orientation exiting the roof.  Later models exhausted at the rear.  Someone else may chime in with specific years the vertical stopped being used.

On my 2000, the Aqua hot and the generator join at the point of change from horizontal to vertical.