Good grief, is your motor home the size of a city bus or an interstate bus?  I'm amazed that you can switch back and forth!  

Stuart
1 1/2" exhaust pipes on my small cars

Dennis wrote (snip):

". . . The outlet of the turbo directly connects to an approximately 8 inch X 5 inch flex pipe. This pipe is almost slinky like. From there is a fancy shaped pipe the connect to the muffler-cat. This is about 12"dimater and 24" long.