With all these other problems now eliminated, and still having this odor in the cabin, we once more put the car on a lift, and smoke tested the entire tank and purge system once more. We found some vacuum anomalies..but no leaks. The fume issue is constant but also intermittent...meaning at times during a trip or while testing we will get no fumes..even with the window cracked. However sooner or later these fumes appear again...however always and only with the window cracked..or either after the car has been sitting for a while.

It seems like we may have a sticking vent valve..the one located in front of and under the fuel tank (not to be confused with the purge valve located between the carbon cannister and the intake vaccuum line as I previously did).

This valve works two ways...to allow built up fumes pressure in the tank to vent out to the carbon cannister, or to allow fumes and fresh air back into the tank when the pressure in the tank becomes negative briefly under load. Our feeling is that the valve is sticking intermittently..but frequently, allowing the tank pressure to rise to where it now vents out of the gas cap pressure relief vent, and then is drawn up into the cabin vent right above the fuel fill door..when the car is moving with the window cracked.

We have ordered a new vent valve, but while waiting, we cleaned the old one and put it back. Test driving the car today and late last night, we are still getting the same thing intermittently, but with very much reduced intensity...again only when driving with the window cracked. Hopefully we are finally on the right track.

Am hoping three other issues which have come up recently may be solved by this...stumbling when cold with what feels like fuel starvation (too much vaccuum in tank), premature fuel cut off (6300 rpms)..again too much vaccuum in tank, and idle surge when backing off the accelerator..idle will stay briefly at 2200 rpms, and then slowly drop to normal (900 rpms)..maybe due to excessive pressure in the tank..which bleeds down as fuel is comsumed, but continues to push fuel into the system due to excessive tank pressure for a couple of seconds...

Well time will tell...I actually had the fuel shut off climb to 6600 last night after cleaning the vent valve....twice, but then it shut off at 6300 again during another test run...we shall see.

Hubris is a terrible thing...