i have a full tailpipe run out the stock location. i also had my 87 with a sligtly turned down tailpipe in the same location and still did it. also, before i put the new system into the truck, it had a turn down and out the side exhaust from the previous owner and still did the same thing.
the only thing ive found to combat the fumes from coming in is to have the rear passenger windows open from the rear side forward. but some still get through.
