UPDATE: I removed the throttle body and adjusted the plate and TPS as outlined. After reassembly the start did not go too well. This is starting with a cool( South Florida) ambient temperature , about 70 degrees or so. The engine immediately died. I started the car again and gave it bit of gas and it held. I kept it like this till the engine warmed up . However once I let off it would grumble/vibrate, at a very low rpm 300-400 or so. While in this state I went to the engine and played with the electrical connection to the IAC valve and no change. Both hoses at the valve were secure and tight. I rotated the throttle pulley and noted that the humming sound associated with the IAC valve was fluctuating and this echoed with the engine vibrating in sync. I disconnected the hose from the air box and there was a strong pull when I put my thumb near the open end. I advanced the throttle pulley and noted a series of vibration associted with a suction , no suction at the hose end . It seemed to me that the IAC was opening and closing randomly at idle. I could actually hear suction come and go with a slight clicks from the IAC.
A while back I had purchased a used ECU to help solve an issue that I had. It turned out not to be the ECU then. If what I understand is correct the ECU provides power to the IAC once the TPS sensor is closed? The ECU then control idle rpms. So was it the IAC ( which I cleaned thoroughly) that was faulty or could it possibly be the ECU sending faulty signal to the IAC? I removed the the ECU and replaced it with the spare . The idle settled down steadily. Turning on the Air conditioning resulted with an uptick in rpms. No stutter or hesitation. There were no shaking after gassing up and backing off a bit. The transition was smooth. I drove around the block a few times , coming to stops , going in neutral and back in gear, turning off and on the air conditioning and everything seems normal at this time and I hope it stays that way. Now what I would like to know is if the IAC modulates during normal operation. The reason I ask is that even when the the revs are up there is still some suction at the input hose. I thought the IAC would close then but apparently it does not. Every IAC that I see for sale on ebay states for Regina systems which my 740 is. This leads me to think that it may not be an either open or close operation that perhaps some other system is. Thank you to all that provided information to help me solve this issue.