findly got my k5 running and it has a code #42 and code #54. what could be steting these codes? the motor is .o40 bored 350. balanced, with 9.2-1 compression ratio, 487x gm heads , 1.50 exh ,1.94int, roller comp 258x, ported tbi and varible fuel pressure regulator. fuel pressure runs about 12psi at idle and crack the throttle and it goes up to 15psi. engine seems to run okay lots of power. i checked for a break in the electric spark timing (est) circuit #423 and it read .60 ohms. so the circuit is not open. i tried clearing the codes but they come right back. i think that i might need a new ecm computer chip. maybe from turbo city.anyone have any info on where to start?