I'm not familiar with the getset location on the LY. If it's curbside I could see why exhaust would collect under your awning. If you haven't already checked the exhaust system and muffler you might want to get under there and make sure everything is connected and there are no leaks around the flange gaskets. It sounds like you could have a leak which catches fumes under the coach. Also, I've seen an exhaust extension tube in the back of Motorhome Magazine that carries your genset exhaust up the side of the coach and over the roofline through a temporary (while camping) chimney.
1986 Airstream 345 Classic Motorhome