Do you use-still have the factory charging system? Do you charge the battery between hot laps-heat race-main event? Could be what the others have said, but also could be a getting low on volts in the battery. Bad ground to pump or to the engine also. When I have had dirty injectors, it will run bad all the time, not be hit and miss. Also when it is a bad fuel pump, they seem to work well or not work at all. The regulator could be the problem. Do you have a return line to the tank? Are the filters in back wards- some do matter what way they flow. It could be some type of heat--over heating of the computer also. Just my thinking.