Just wanted to let the forum know that after 1 year on an Autozone/Wells cap and then my many hours testing etc - it was the cap internally (in the plastic traces pins to plug wire outlets) arcing or shorting and it does not show inside. So you have spark at the coil and out of each wire/plug, fuel pressure is good, all relays and fuses OK, all scans OK and it still won't start!! Yes, GM then puts a cap/rotor on and that was it. Talked to a Ford mechanic and he had one recently too. Beware of the aftermarket caps!!
Buy Delco, dealer brand, or premium like Accel. Let us know who else got caught on this!

Crap I just put one on too.

anything electrical i go acdelco, Fuel pump, cap, rotors, wires

I had the same problem (with an Autozone Cap), went with the NAPA Premium cap and its been great.