[Walker]

My exhaust goes out the back not the side.
I have never experienced the problem with the canvas down but, mid summer, who wants to run with the canvas enclosing the cockpit.
I have a factory hardtop which is the best thing since apple pie.
Also, I have tried various combinations of opening and closing hardtop hatches and the center windshield vent.
It seems to be a factor of speed and wind direction from what I can see.
I have learned that air coming up over the bow, crossing the hardtop and then rolling down and over the transom causes a backdraft of sorts which rolls forward again into the cockpit.
Seems like an aerodynamic problem.
Hope there is an answer somewhere.