When I read the title, I figured you needed a good dose of beano. However, you really do have a problem here.
If the smell is coming in while you are sitting still I would suggest you have a slight leak at your fuel rail, possibly around the injector o-rings or regulator/lines. One way to tell is to open the hood and have somebody cycle the key. A small high pressure leak will slip out under pressure and make the injector/fitting glossy for a moment, then fade back flat as it dries. At an idle your static pressure on the rail is the highest and it drops as you acclerate and more fuel goes through the injectors. Once you have isolated the leak you need to fix it asap.
If you are getting the smell drift in as you pick up speed, it is highly possible you have a leaky gas cap, or the seal between the tank and neck. As you move forward you may slosh the fuel back causing it to spill out a tad. The way the wind travels around the car it will actually suck some vapors back into the cabin through any leaks in the rear hatch weather strip, or even the bulkhead seal for the rear harness (if it is not in tight). After you go down the road a bit the liquid evaporates and there is no smell when you come to a stop.
Does it only do it on a full tank?
Finally, you may find your charcol canister is ready for replacement and can no longer filter the odor in the vapors.
I meant to say when you turn the key to run, but don't start the car the fuel pressure spikes in the rail. It drops as soon as you start the car as vacuum starts activating the regulator and it will adjust as you accelerate. The pressure goes UP upon acceleration, but the strange factor is your injectors are releasing more fuel at the same time.
I also wanted to add that if you have a pin hole leak in the regulator diaphram, fuel will get sucked into the intake and it usually stinks pretty strong, but you can't see it because it is all running in the vacuum line. An easy way to tell is to pull the vacuum line off the regulator, turn the key, inspect for the glossy exposure of fuel out of the vacuum port, etc.