Evap Cannister thread
Check this thread and see if any of it pertains to you. This guy found that the evap return line had fallen from its clip and was immersed in fuel causing all sorts of problems. I would suggest blowing out the evap line and checking your charcoal cannister. If you need a cannister, check with this guy as it sounds like he has an extra. Your fuel cap should hold pressure and release on vacuum, so that should not be a problem here. Let me know what you find. Aaron