Trouble codes...

Code 15: Low Temp Indicated. It either means that the CTS is bad, or that the CTS connection is bad. (well, those are the nice options). If you BOIL (212*) the temp sensor (tip) the resistance should be 177ohms. If you FREEZE (32*) the temp sensor (tip) the resistance should be 9420ohms (9.4kOhms)

Code 44 lean exhaust. Sure it wasn't 45? That would make sense, as low coolant temp would cause the ECM to dump more gasoline into the mix and cause it to run crappy.

Besides those codes, what are the symptoms?

GMC Gremlin

Hold on, isn't this your ginormous 4x4 you've spoken of in the past?

GMC Gremlin

YUP!!! It IS the same Pain in the Gas and it WAS code 15 and 44...

I replaced the entire throttle body off a running but HIGH miles engine. the only thing that improved was the idle quality. If I turn the key and don't crank it right away, it loads up(bad FP regulator?), it still hesitates, cranks allot before starting, and gets WORSE mileage now! AAAARRRRRGGGGGGGGG

I am gonna pull the new FPR from the other TBI and the new IAC valve and see what that does. The main body of the 'new' TBI is better cuz the butterflies aren't open a 1/16th of an inch now. I think that's why the idle is so much better.

I would think bad heads with the exception that there is nearly 20inches of nearly perfectly steady vacuum. I am thinking maybe the cam is going flat? Any opinions on that???

I think you answered your own question. I think your ECM is dumping a shit load of fuel into the mix and causing it to run like shit, get bad mileage, and possibly the loading up. So, I'd try a new CTS. You can simulate "heat" by shorting out the wires. You might freak out your ECM into thinking the engine is over heating (I don't know if it will care?) and see if it stop dumping masses of gas in there, that way you aren't throwing parts at it. I wish you had posted this sooner, there was a low-miles TBI setup on ebay sold for like 30bux, I almost bought it just to have it!!!

GMC Gremlin