I do not, given my experience with my own trucks. If you follow the procedure listed in the manual to close the IAC, verify you do not have vacuum leaks or pirate air then I'd verify base idle. If it's low, I'd adjust it. 650rpm seems pretty high for base (What OP adjusted it to). So if a person does that and still has a problem, you leave that in spec and then move to the next possible cause. If the thing is hunting for idle without the IAC adjusting counts or disconnected and we've already verified it's not pulling in pirate air, I'd look elsewhere. Like Schurkey said- it's time to look at the datastream. I'd like to verify fuel pressure when it starts acting wonky, look at MAP values, see if it's popping in & out of closed loop and look to see what the O2 sensor is doing when it runs like that. Would be nice to also verify the TPS isn't reporting bogus info to the ECM as well. Schurkey has also posted somewhere else about how to check for a misfire and how to gauge each cylinders' contribution by slipping small, blunted nails under the plug boots at the distributor cap and grounding each out individually. I'd try that chit and see where it got me. Another time I had an erratic idle, it was caused by the TPS. The idle would hunt, or just stay a bit higher and then drop. Step on the gas, ease off the clutch in gear and it was fine. I connected my brick to it, took it on a road trip and got it to act up. Sure enough, the TPS value was changing despite my foot being off the throttle. The IAC opens a bit when it does this. Replaced the TPS, problem solved.