My '02 Subaru WRX won't start up after I refuel.?

My '02 Subaru WRX won't start up right away after i fill up with gas?

I blew my engine, I had a 2.0L now i have a 2.5 block. It runs amazing, until i fill up then it wont start for a bit. But once i start driving it runs fine. The code on the reader said loose gas cap, i went through 3 of them. then replaced the MAF now it runs worse, and stalls every time i push the clutch in, and it has a rough idle now! I took the reader to it again now it says misfire on #2. SOMEBODY PLEASE HELP ME!

The big picture is; Why does it not start when i fill up with gas but it is fine until i have to fill up again a week later.