2000 Toyota Camry will not start

I have a 2000 Toyota Camry, 2.2 le 4 cylinder, I am having a hard time getting the car to start.

The fuel pump, fuel pressure regulator, fuel injectors, and fuel filter have been replaced.

The coil packs, spark plugs and wires have been replaced.

The camshaft position sensor and crankshaft position sensors have been replaced. All in the last two days. Plus oil change. All oil seals have been replaced.

Idle air control valve and air fuel sensor have been replaced.

The car was running fine and the next morning it wouldn't start. So started replacing everything.

When trying to start the car if it's given a lot of gas it will eventually start but also sounds like it's back firing. Once the car cools completely off it will not start again. I don't know what else to do.