90q climate control stinks

["Norman, Paul (FF-IS)" <Paul.Norman@us.millwardbrown.com>]

My 90q with climate control stinks of exhaust fumes whenever the car is
stopped and the climate control system is on. If it's off, there's no
problem. If the car is moving, there is no odor as far as I can tell. The
exhaust system is very quiet and well sealed, and there doesn't seem to be
any sources of exhaust leaks when poking around the outside of the car. 

Where does the system draw in air for the interior? Any ideas where the leak
may be?

Thanks,
Paul
90q 20v 
86 944