you're in cali on 91oct, with a built motor, mods on the car without a tune.
the car is most likely pulling a crapload of timing.
also, with teh age of the car you most likely need a need 02 sensor.
we really need logs and data to diagnose anything.
but with R&R of a motor it could be a million different things from a leak to something like a coilpack isnt plugged in.