So I have my 2000 Pontiac Grand Prix gt. It seems to run great other than a slight leak on the oil level sending unit. The issue I continue to run into and can't seem to pinpoint is why it constantly has trouble starting once it sits for a little while. If I started it from completely cold it fires right up without a problem. However if I go to say a grocery shop for a few minutes and I come back out and the engine has gotten above say 155 degrees it has a sputtering start and over 165 or so it won't start. I know it's a fuel issue since I bought the fuel line pressure gauge tool however I'm not sure if its the fuel pump or some sensor. The only way I can get it up and going is to basically stomp the pedal to give it enough fuel pressure. I'm not sure if its fuel pumps because I'm on pump number 2 right now and if anything this ones issue is worse. I have a rather large sound system that's grounded in the trunk. I can't see how that would affect it but I'm kinda baffled. Any help would be appreciated. I don't want to be late to an important event because of this.