I've tried to fix my hunting idle for too long now.
Starts to hunt when it gets to about 165 water temp, before that no hunting.

If there was a vacume leak, wouldn't it hunt right from the start? Or only when going into closed loop?
I wired up the s200 myself, and with no codes being thrown now.
The purge light is lit up on the side of my datalogger software, and I'm not sure what that is indicating. But other than that, it's reading just fine.

Could it be the ECU or still vacume?
I have the IACV holes in the intake mani blocked, but the sensor is still hooked up to the ECU, and has coolent running through it. Am I my own worst enemy here??
Point me in the right direction guys... thanks

 

If the air holes between the tb and fitv are not plugged, and the fitv has it's coolant bypassed, then yes. Get some solid gasket material, a piece of sheet metal, and sandwich it between the tb and the fitv.

 

What engine is this - GS-R? Do you even have a FITV?

Yep - the ECT needs to show a hot engine before the ECU ever tries to engage the fuel cut on decel strategy. This is why your idle doesn't hunt until around 165*.

With the engine warmed up, remove your intake and unplug the IACV. Is there any air being sucked through either of the two holes (assuming GS-R) in front of the throttle plate? If yes, which one?

There should be no air being pulled through either of those two holes. With the engine hot, the FITV is basically disabled. With the IACV unplugged, its closed down and thus disabled as well.