my car is hard to start and initially runs rough every time i fill up with gas

my 2004 sonata (6) just started doing somthing similar. Does'nt matter if you have a half tank of gas or you fill it, when you go to start the car, it stalls out. Then you have to start it, hold the brake and gun it to keep it running. After that, no problem car will start every time. Think its the cannister purge valve or cannister close valve or are they the same thing.