Hello.

Z32 '94 TT M/T w/ AEM 30-1620U + AEM UEGO failsafe AFR/boost gauge + MAP sensor + EGR delete kit.
Put in NGK plugs, replaced injectors [#5 crapped out] & put new PCV valves before getting the EMS installed and tuned.
Also replaced most of the vacuum lines, except the ones on the turbo actuators.

Engine will stumble/hesitate on idle [not under load] 6-9 minutes after a cold start, this last about 2 minutes or less after that everything is good.
Before the standalone EMS, the engine would stumble/hesitate on idle but it was more erratic, also happened while coasting.

I dont have a dummy MAF put in yet; dont know if that would affect the air flow enough to cause an issue.
Anyone has any ideas as to what could be the culprit?

Thanks.

IACV most likely is your culprit, with the CTS connector and PTU harness corrosion issues the next bet.
The fsm will help with IACV testing, and a visual inspection of the connectors for green crud seem to be your next moves.

IACV I would recommend as well. I also had a similar problem with my NA. Have you also ruled out fuel being the culprit? Not just the injectors, fuel filter, or fuel pump, but the gas in the tank itself?

UPDATE:
IACV-AAC motor has 0 ohms=bad
IACV-FICD solenoid valve does not click=bad
IACV-AIR regulator has 75.5 ohms=good

Plungers and springs are good. Found sulfate on the AAC motor connector terminals. A bit of carbon in the IACV valve body.

Thanks for the help.

UPDATE on the stumble of death.

Last year, replaced the IACV with new unit, old regulator test good, checked variable timing plungers, fuel damper, regulator, fuel filter (found some fine metal shavings on the inlet from the pump). Took out the fuel pump, was going to do a flow test, but opted to just put a upgraded more modern unit.

Checked the fuel pump control unit for damaged components, found nothing there. I'll report once I get her running.

Issues: bad stock CAS sensor ( it would only act out around op temp) AND ground and power wires broken inside, also a bad PTU.