I have a 96 K2500 5.7 Vortec that was running perfectly. However, for the past week, it starts up normally but when I try to start it when it's warm after it's been off for 5 mins, it won't fire, it just cranks. When I release the ignition it will fire and choke a little sometimes. I'm not touching the gas. I've found that to get it started, I have to press the gas to about 3/4 and then it will start to fire, sputter, then start. It will run rough, then hesitate if I hit the gas hard. After a while, no hesitation on the hitting the gas hard. It's back to running normally. It's almost like it's a flooded carb. I replaced the fuel filter 6 months ago. The rest of the truck is original and it has about 160k miles on it. Does a fuel pump behave like this before it failsl sometimes? Injectors? I will be replacing the dist cap, rotor, wires and spark plugs in a month or so. No codes. TIA.