The wires gave more power but more backfire and stumbling. The coil made it overkill. I have a muffler just no cat, straight pipe instead of a hallowed cat shell.

 

How are your grounds?

 

The taped up box thing is stock and should be there. Does it back fire when you're on the throttle or when you're letting off? I'm assuming since you said you missed 3rd gear that you have the M6. Get the car to do it and as soon as it does depress the clutch to put the car in neutral and report back on whether it still did it or not.

 

There is a possibility that when you missed the shifts you over revved the engine and bent something in the valve train, which would account for all the backifire. Aslo, the opty does not like tobe over revved and internal parts can fly apart, including the extra large rotor.

 

Have you tore into her and found the problem yet?

 

i would look at the opti and the ignition control/coil module. the rotor screws can come lose and mess things up also the rivits on the rotor can fail and it can also mess up the spark delivery. black box is a resistor for the tach. the 93 is the only year with it.

 

Car doesnt back fire at all in neutral, only during loaded downshifts, and prolonged non throttled coasting in gear (2nd, 3rd, 4th, sometimes 5th but not 6th) It starts missing/popping over 3K in low gears, but has ZERO problems before as long as throttle is applied.

 

I thought about that, but I missed shifts when I first got it, maybe 3-4 months ago, the problems i'm having now just started within the last two weeks

Not yet, Im trying to eliminate all the other possibilities before i go to the opti. Since I dont know how old it is, im thinking of just replacing the whole unit, car has 115K on it and it was bone stock when i got it, minus typical tune up items.

Good as far as I know, I haven't messed with any. I know the one near the coil is still grounded

 

Checked wires, all good, fuel pressure stays above 40 throughout the RPM range and with FPR disconnected. Gonna try to put my old coil in and see if it makes a difference.

 

That's what I figured you'd say. My car does the same backfiring if I'm in 2nd or 3rd and above 30 mph and coasting. If I'm not mistaken that's normal for the car to do because you are at a high rpm but low speed. If I put mine in 4th (I have a auto) or neutral, or I speed up in the low gear, the back firing stops.