My 2 cents is that I had a similar problem in my '71 Standard Bug and it was the fuel filler hoses. Mine would smell only when it was filled up and especially after a sharp turn. On mine there are a couple of lengths of big hose connecting the filler collar (my term) to the fuel tank, plus a few other small hoses running around. One of the smaller hoses was damp when I checked right after a fresh waft of gas fumes made me pull over, so I replaced that. It wasn't enough, even though I never did see any dampness on any of the other hoses afterward. I next replaced all the hoses I could see relating to the filler system and that fixed it. No more stinky.
By the way, I did not use stock VW rubber as that was pricey and I'm not convinced the OEM rubber is always the best in all situations. I just made sure the hose was fiber-reinforced and fuel-rated.
Keep yer hands on the road and yer eyes upon the wheel.