Chevrolet Repair: 5.7Lt TBI starts but will not idle cold, ohm meter, speed tranny

Question
I have been chasing this problem for a while and it is getting the best of me. Here is what's going on. I have a 1991 K1500 with a 350 TBI and a 5 speed tranny (5th is OD). The truck sat for about 6 months and was not driven very much. The first problems started with hard starting. It would crank and crank and crank before starting. Once it started it would not idle until the engine warmed up. It would run fine after that. There were no OBD codes at that time. That problem developed to a point that once the engine got to normal operating temp and the engine was turned off it would not start until it cooled off
I posted the above and I received a suggestion to check the coolant sensor which I did. The ohm meter showed that it was working OK but I noticed that if I unplugged the sensor it would start fine but it would still not idle until the engine got close to operating temp. I then shorted the sensor plug by sticking a paperclip into the terminals. I found that it would idle fine (but at about 1200 RPMs)now but was really hard to start. Now I was getting a code 15 and 14 (both were expected because of the sensor plug).
After replacing the sensor it pretty much went back to the way it was before, started OK but would not idle until the engine started to warm up (not quite to operating temp) and then it would idle at ~1200 RPMs. Once the engine got to operating temp the idle would drop to ~800 RPMs. I drove it for a day like this. I noticed that it started to show a code 15 again (I did erase them from before)
The outside temp dropped to about 20 degrees and when I tried to start it, it would just crank and crank and crank. I was told that when you jumper the OBD port to check the codes it also sets the IAC to open all the way. I did jumper the port and could hear the IAC vibrating and I unplugged it. I tried starting the enging and it started right up but would not idle at all. The only way to keep it running was to pump the gas pedal. I kept it running until the engine warmed up some them I reconneded the IAC. The truck would idle OK but again at 1200 RPMs and I still get a code 15. I did also notice that sometimes the engine sounds like it is hunting. The idle will slowly jump up to about 2000 RPMs then slowly drop back down to ~1200 RPMs and sometimes it will drop down to 800 RPMs. The truck drives fine but it will every once in a while start jerking if the gas pedal is stomped on and then there is that code 15. The wiring for the coolant sensor is OK. The flow charts I have seen say the next step is to replace the computer...suggestions please

Answer
Hello Ward,

Before replacing the computer, I would check the fuel pressure, (sometimes a pain on a TBI, but there are several adapters) and make sure it maintains 12 to 13 PSI. I like 13.
If that stays up there, test the throttle position sensor.

On another note, you are checking the coolant sensor for the ECM, rather than a sender for a guage, correct? Sensor for the ECM should have two wires, but I assume that is the one you are checking since you jumpered the connector.
Did you get the sensor readings from Chevytech on chevytalk.com?

Also, have you cleaned the IAC port, and is there any chance some insects, like mud dobbers, have it partially plugged?
Van