84 Turbo High Idle

Normal idle for a 300ZX with M/T is 700 rpm plus/minus 50 rpm at sea level. When I first purchased this car, it was idling at 1400 rpm. I replaced the Air Regulator, had a gasket replaced on the Idle Air Control Valve (IACV), and made some adjustments to the idle. The most I've been able to reduce the idle is down to 1000-1100 rpm.

I have performed diagnostics and made adjustments according to the FSM. I even tried swapping in another ECU and a known working IACV from another car. I sitll couldn't get the idle back to normal. From what I know and from what I read in the FSM, I have exhausted all of my options at this point (other than deleting the IACV). Would appreciate any information from forum members who have a lot of experience with engine performance or idle speed issues.

Cheers