1997 Subaru Outback

Smells problem
1997 Subaru Outback 4 cyl All Wheel Drive Automatic

I think I have submitted this question a couple of times and do not seem to get a response, even with a donation. So here goes again, maybe somebody out there can help me. I changed the motor in my car, put in a 2.2, better mileage and now I smell gas. I smells of raw gas, but I believe it is fumes because it is not venting properly. But it only smells when the car is being driven, mostly on take-off and the windows are down. It is not coming into the cabin from the engine, it comes in from outside. It does not smell when idling. I get a 0440 code and have replaced just about all possible parts according to the code. So far I have replaced, the vent valve, pcv valve, the fill pipe, purge lines. I could really use some help here, as my mechanic and I are both dumbfounded.