Although not installed in a Chevy truck, I recently dropped a built TPI out of a Vette into a FJ40 (pics below).
Have you tried to read the codes? As an example on my truck, there were some problems, but the check engine light wasn't on. Turns out that the check engine light was improperly hooked up, and the computer spit out a LOT of codes when I read them with a scan tool. Addressing all the codes one at a time got it running just fine.
From everything you are describing, it sounds like it may be Air Temp Sensor either on the bottom of the plenum or top of manifold towards the rear (by distributor).
