you bring up a very good point about the exhaust. Until I have someone with the same exhaust design I want know how my top works with it and the fumes issue. I believe the W/S are a big contributing factor when combined with a top. Jeep tops can do the same thing with doors off and the rear window up.
I run the alpha side exhaust. No problems with exhaust fumes in the cabin. My understanding is that getting the exhaust into the side slipstream where it doesn't get a chance to come back around is what's needed. Because the welter duals are already where the air is coming back around that Vortex effect that I mentioned before sucks the exhaust right back into the cabin, just like it does rain.