1988 town car hesitates at a steady acceleration and misses and back fires at idle. I'm getting 51 and 31 codes with the key on engine off test and 12, 13, 21 and 74 codes in the run test. Ok the 12 and 13 may be connected to the 74 BOO switch codes but my brake lights all work. For the codes 21 and 51 the temperature (ECT) sensor has voltage and varies.

Would any of this cause the hesitation while driving?

I've replaced the fuel pump, fuel regular, EGR, air by pass valve, hoses to the plenum and fixed a vacuum leak to the thermoactor solenoid and still she jerks and misses. Help!