Also, do a search on the archives. There's several accounts and good advice to be had. I've had this problem for ages, and it's taken me for bloody ever to rectify it. The last piece of my puzzle is my valve cover breather; it is blowing straight into my weber airbox assembly. This in turn is wafting a very rich smell (from the webers and exhaust) back into the cabin, especially when the car has been stopped. Prior to this, I've had my tank checcked to ensure it holds pressure, no tank boot, rerouted the breather to come out by the license plate, marine sealed fuel line now connects the tank to the pump, pump to the webers etc...50% of the 2002's I've had suffered this problem. Sometimes its an easy fix like a bad tank seam or crappy fuel lines, other times, it's more complicated. Thinks that make a huge difference:
1.) Good trunk seal
2.) Good fuel line (if it runs through the cabin--either marine or steel)
3.) Good Hood seals
4.) Sealed Tank
Email me if you get stuck
Toddman