Easiest thing to do would be this:
Get yourself a 1996 SSEi engine harness...or modify yours for the additional wires needed for the supercharger...not hard to do, just find someone with wiring diagrams...it'* really not hard at all.
I'm not really familiar with the differences of MAP sensors over the years...but it seems likely to me that one from a 96 should fit in it'* place. My thinking is that the connector is different simply for the newer style PCM of the 99. If I'm wrong hopefully someone could step in and correct me.
Once you do that, you can flash your 96 PCM with the tune of a 96 SSEi. A dealer can do this for you, if you can't do it yourself. This should get everything running properly and allow you to still drive the car. There is a "but", though...
The gear ratios between your trans and the SSEi trans aren't the same, meaning the shift points will be off. It should still operate and function acceptably as long as you are gentle with it (in other words, no redline!). That will need to be custom tuned, unless you swap for a different trans.
This is my thinking, as in 96 both the SE and SSEi used the 4T60E transmission...only differences were in the gear ratios and differentials. Thus the pinouts between the two PCMs should be the same, with the exception that the SSEi has additional pinouts for components like the boost control solenoid, which you can add yourself.
This will get you on the road to a proper running engine, after which you'll just need to calibrate it for the proper gear ratio. Just remember not to drive it too hard until then.
I won't deny that I am a little unfamiliar with the 96, so if anyone else could confirm or deny this, I would appreciate it!
- S10 - The luxury truck - 4.3 Vortec V6, 68,000 miles, 3.42 gears, leather, wood, sound, HID projectors.