I am running the same "roll over vent" that BW is. I just have it venting to the atmosphere as is and don't smell any fumes from it. Just those from the exhausts. Not to mention the smell of melted rubber from the tires.
I think that if the car is stinking up the garage with gas smells, there are larger problems then that?
Why can only the wife smell it and not you? Don't answer that. It is a leading question.