I am working on getting my 740 straightened out and it is starting to drive me nuts

Its a 1990 740GL non turbo automatic
Regina system

I am getting 2 codes
1-2-2 Air Temp Sensor
2-3-3 Idle Valve Closed

The problem I am having is rough idle and high idle, in park if i open the throttle a little it will stick at 2000 rpm after letting go. After about 30 seconds at that high of an rpm it will start cutting out and dipping to 1500rpm then swings right back and it will do this until I put the car into gear. When in gear the idle drops to about 900 rpm but is very rough.

I removed the hose from the IAC and block it with my thumb and the idle will smooth out, if I unplug the IAC the idle will smooth out too. I drove it unplugged and noticed a lose in power from the car and when put into second gear would backfire at 3000 rpm

I have done plugs, wires, cap and rotor on the car already. I also have replaced the fuel filter. There is no cat on the car so I dont have to worry about that.

I did try to clean the IAC and the valve moves back and forth smoothly i have not tried to look at it when applying power yet though. I feel at this point I am going to need a trip to a junk yard and see if I can find a IAC or 2 to try out and see if that clears it up.

Any suggestions on what else could be causing the idle issue? Also is there a way to test the Air Temp Sensor with a VOM? I don't want to go replacing it for no reason.