Car Stalling When Warmed Up and Idling

My car, when warm and driven for a while, stalls out and doesn't restart till car is cooled back down. You can smell gas after the restart. We've cleaned the Catalyc Converters and the MAF valve when taken off will shut my car down so we don't think that might be the issue. It starts perfectly fine when she hasnt been run (First start). What might this issue be? Some of my friends are also saying a gas cap cause I havent had one on there for a month or so, but I dont see that causing this big of an issue.
I have also always had issues with the fuel stem area as far as pumping gas, but I also doubt this is an issue.
A lot of people have pointed it out being a gas issue but we have yet to figure it out, and I am becoming overwhelmed with having to wait for it to cool down before it starting again. Please Help.