After driving my car for 20 minutes or so, when you exit the vehicle and go back by the gas tank you can hear the tank trying to suck in air at the filler neck. When you remove the gas cap, air gets sucked in quickly then stops. Seems to be affecting the fuel delivery some, because after driving it for awhile the idle at stop becomes rough and occasionally dies. If restarting it immediately, you have to hold the gas to the floor to get it to fire. Let it sit for 15 minutes and it fires up fine and all effects are gone. Runs fine at any stable speed on the road. Any thoughts on a fix?