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When you try to start the car when your parked if you Hold the Throttle Wide open and the car starts does it keep on running smoothly or does it die after it starts?If It dies it sounds like a Fuel pressure regulator problem if it keeps on running and drives fine afterwards sounds like you have big injectors and its not tuned right or your MAF may not be calibrated to the Injectors perfectly.
When you have to hold the gas petal Wide open that makes the computer shut off all fuel going thru the injectors thus leaning the mixture out if the car WAS flooded.That cleans out the Overly rich mixture till it starts.Alot of guys have this problem when running 42# injectors and higher if their cars arent tuned for them especially in Hot weather its called Hot Starts.
the only way to get the car to start is hold the throttle wide open if you you let off it stalls there is no in between full throttle nothing at all.
sooo, is your car stock? if not, i think we need to know wut heads and "compression", cam, adj. fuel pressure regulator or not, current fuel pressure, injector size, mass air meter size and calibration. i think sum of this info would us help u more efficiently and reduce guesses.