Thanks for the info Mark. What confused me was that there was a knock sensor on the 454 and factory wiring to the third (now removed) plug at the ecm. I would love to experiment with tuning and burning but I don't have the equipment for that and this is my friends truck so I think I will let someone else have that job. If it were up to me I would have got something like a Megasquirt ecm. Dave, I have no clue which bin is in there. It is the stock ecm from the 1991 GMC 3500. This is what I do have: ecm = 7747 other numbers on ecm are 86ANTY K383480987 and the software reported the PROMID = 8221 hope that helps and if you guys do any tuning by mail let me know. This is not a max effort deal but rather looking for something like Mark described. Lean the idle a bit, I think the injectors are a little large for the 402 in open loop. Advance etc...

Thanx again!