2000 Tacoma, high idle, no codes

2000 Toyota Tacoma 2.7L M/T Federal Emissions, factory intake/ exhaust no aftermarket items that i could see. including air filter.
customer brought in the vehicle with a high idle complaint. the customer is a DIYer and bought the vehicle couple months ago with a blown head gasket, did the repair himself and ever since the vehicle has idled at about 1200rpms, (should be 650-750rpms). customer replaced the IAC valve, no change.

This is where it became my problem.

I scanned the truck for codes and there were none, pulled up data while the vehicle was cold (todays average temp was about 10degrees) ECT agrees with outside temp, started the engine and watched coolant temp warm up to 190 degrees and start cycling as it should. no change in high idle problem. checked TPS and idle switch, both reading within spec. made sure vehicle had entered closed loop (it had). looked at IAC duty cycle (24%) i believe this to be the lowest value the computer can command the IAC to (please correct me if I'm wrong). used scanner and commanded IAC duty cycle to change while watching requested vs. actual, they always matched. bidirectionally i could command the IAC down to 11% and it did lower the idle, but only to about 950rpms. pinched off the IAC air supply hose and the vehicle dies instantly. hooked up scope to IAC control wire and verified computer is controlling the IAC and changing it when i add a load. removed IAC valve and bench tested it, it does open and close, when closed i can still blow through it, but it is quite restricted, I don't know if it should seal completely or not. reinstalled IAC, checked fuel trims, total trim (-3%). checked O2 sensor feedback, sensor was cycling and responded to a vacuum leak i created. test drove and did some WOT pulls VE was (88%). pulled out the test light and checked engine timing (10degrees). questioned the customer and discovered the IAC he bought on ebay from China, i told him to clean the original IAC and put it back in to see if there was any change.

I know i missed some things, please chime in with them. this one had me running in circles, (probably because i listened to the customer and not my gut) this just sounds like a simple IAC, but what are the odds that the truck would have a high idle, replace the IAC and have the exact same problem, but the IAC actually responds to commands. let me know what you think.

First thing I'd do on a Toyota with that history is check the vacuum lines have been hooked back up correctly. That truck probably has a vacuum actuated throttle opener on it which holds the throttle slightly open for starting. Also vacuum controlled EGR. If those lines are crossed up it could be allowing some air to bypass the throttle at idle.

I did see the vacuum actuated throttle opener, but at idle there was always about a 1/4 inch gap between it and the stop screw on the throttle shaft. when i snapped the throttle it would move, so it appeared to be functioning. I also took a look at the vacuum lines they all appeared to be in good condition and to go to the correct locations R went to R, P went to P, and so on... I wish i could have found a vacuum diagram for it to be 100%, but I didn't have any luck locating one.

However, the customer happened to come in this afternoon, and said he cleaned the old IAC and put it back in, the truck now purrs at 700rpms.
I'm so glad that fixed it, now i can sleep again. I guess this is a reminder to not buy cheaply made electrical parts. Thanks for the feedback Matt.