Hello together!

First, I'm from germany, sry about my english. I have a kitfox III with Rotax 582 greyhead with aluminium wing and headertanks.
I haven't got any fuel or oil smell in my cabin, not in hangar and not during fly. But I have a little exhaust smell during fly and after fly, my clothes smells like exhaust. I checked my exhaust system (original Rotax muffler) and the way out of the cowling, the end of the system is longer than the original, I modified it with flexibel alu tube. I checked the firewall, I seal up my doors with rubber and I seal up the holes in bottom.
Is it possible, that the Prop washer pulls the exhaust by an another way into the cockpit, may be throught the turtle-deck? Has anybody further ideas of ways the exhaust could get in?

Thanks

Olaf