Just completed a 5spd swap on the vert, took it for a drive today and under hard accel and decel it backfires pretty bad, now the tranny is out of an 89 i believe so i have tried using the auto ecm with a 89 5spd memcal as well as a manual ecm out of an 88, no difference, not sure where to go now, also I dont have wires for the vss signal so maybe i should just swap in a 5spd wiring harness but that's probably for another day

Is your check engine light on? If so what codes are it throwing?

nope no check engine light, nothing to go by other then teh fact that the car never did it before the swap, idles fine, so this is what makes me believe it's a computer issue but finding an 87 5spd ecm up here is really difficult

87/88 ecm's are the same, however 89 went from maf back to map only. now why isnt your vss wired up??? 87 should have just an electronic vss with no cable. your wiring should be on the passenger side of the car were the vss would have been on the auto. lengthen those wires and get it hooked up. i doubt this is causing the issue though.

i doubt its a computer issue. is it backfiring through the intake or out the exaust (through the intake will sound like a pop from under the hood).

the vss out of the auto tranny was actually not electronic but only cable driven (and alot smaller in size), but it's backfiring out the exhaust so I guess it's possible I have a sticky injector, and it's dumping too much fuel, didnt have this problem before the car was parked though

all wiring grounds are where they are supposed to be, I think the plenum is going to come off tonight to check the vacumm lines underneath it, although a leak is not being heard but who knows