My son has a 95 C1500 that started having problems. Bought a motor out of a 95 Tahoe. Both are a 5.7. Motor in Tahoe drove and sounded great. Put the motor in my sons truck and now it won't run worth a crap. Idles way high one minute and too low another. Put it in drive and motor stalls and dies. Sat for two days and now won't stay running at all unless you keep your foot on the gas. We've swapped TPS, MAP, EGR, IAC, TBI, knock sensor, new plugs, wires, cap, rotor, and coil. Waiting on adaptor to check fuel pressure but looks like a good pattern at TBI. Timing is good. Thinking maybe ECM as I'm getting conflicting codes. TPS low voltage, map low voltage, map high voltage. Any thoughts?