[Just call me Sean]

There isn't much to the engine control system on these trucks and since you did most of it I also would suspect something with the distributor. I've had bad ICMs and pickup coils do strange things. Other than that, it might be doing what my truck was. Mine was dumping the maximum amount of fuel it could into the motor due to improper oxygen sensor readings. The oxygen sensor was good though, I had to add grounds everywhere to fix it.