'06 A4 2.0T quattro with about 72,000 miles - bone stock

So a few months ago my check engine light comes on. I take it down to the shop to pull the codes and its the evap. Smoke test the whole system, cant find any leaks, no signs of leaking gas etc. I figure maybe its just a bad gas cap or something stupid.
But ever since that light came on, Ive been having problems starting the car after filling up at the gas station. The only time it happens, is right after filling up. If the car sits 3 days in my driveway, it still starts right up. If i shut it down after I finally get it running at the station then restart, it fires right up. Ive tried only running the tank down half way before filling up, and the same thing happens. I even turn the key on, wait for the fuel system to pressurize, then start it, and the same happens. It cranks for about 5 seconds or so and when it finally fires the engine stumbles until i give it a bit of throttle. Then it runs fine...until I have to fill it up again. Im thinking maybe the fuel system is losing its prime somehow...but why would it ONLY happen after filling the tank???
Any ideas/suggestions/help would be greatly appreciated.

 

Changed the N80 evap purge valve, problem went away. Thanks for all the input.