Ever get any exhaust in the cab issues with that? I know you aren't supposed to run them straight out the back due to the rear window sucking the fumes in if open. Mine are the stock dual setup exiting to the sides behind the rear tires and I still occasionally smell exhaust.
Duals out the back make this problem worse. When i had my 94, with the lift up rear window, you couldn't drive more than 15 min with the back window open w/o getting fumed out.
The burb isn't as bad, but i agree, this is not an idea setup for driving with the window open. In our 90 with stock exhaust, we drove about 4 hrs before we noticed the fumes. I know i would notice faster on mine with duals.