On my 300E, I occasionally had this problem. First, I changed the gas cap. Then the fuel filter. But, sometimes it is just bad gas. I had a really potent gas smell one time and my mechanic drained the gas and I went back to the gas station and I got a refund. This was 7 years ago, gas has become much better in quality. Perhaps, you got some fuel that was in the underground tank that was over 6 weeks old. Usually, this is caused by low turn around caused by low demand of 91 octane.

As far as the system over pressurizing, I've never heard of such a thing, but it probably can happen. Don't fill the tank up more than 1/2 because you don't want a catastrophe happening like an exploding gas tank. Maybe, you just overfilled the tank. It is always a good idea to know your fuel tank capacity and reserve.