Fill it up & it won't start?!?

I have a 2003 Kia Optima V6 with 100,000+ miles on it. Ever since i’ve had it (used) when i fill up the tank it won’t start unless i put my petal all the way to the metal & keep the RPMs up around 2000-3000 so it won’t die. Doesnt matter how much gas i put in either. It could be $5 worth or $45 worth. Ive tried lettin it run, taking gas cap off, changed the spark plugs, replacing the gas cap, Putting heat in it to get water out. It runs fine after i get it going though. Im stumped and so are the mechanics :frowning: Any help would be much appreciated. You can email me at THANKS!

have the purge valve checked,then go from there.

Where is that? In the engine or the tank? Thats the first time i’ve herd that one. Thank you!

on the plenum,underhood, at throttle body,or at the bulk head. plenum side.