Ive noticed when the A/C is on and reversing while making a turn causes the XJ to start dropping revs and then stall the sharper turn you make.

Something to do with Steering pump - too much strain somewhere?

Would replacing MAP sensor fix this or is there a switch to keep the revs up (Ive read that like on the A/c unit)

I had a look at the IAC motor - it looks like its had it but cleaned it p with brake cleaner. (130,000 miles - never been replaced) In Drive, it revs steady at 500rpm.

 

Not the MAP sensor. Last tuneup with plugs, wires, cap and rotor?

 

Did the plugs with the right gap, new leads and distributer 2 weeks ago. Air filter changed too.

Could it be a vacuum leak somewhere? The rubber o ring around the throttle body where the resonator sits on top is ripped though.

 

I would look at a vacuum leak. Replace the cracked boot and then look around to see if you have anymore vacuum leaks. Also look at the vacuum reservoir behind the front bumper.

 

Is the clutch on your ac condensor good? It might be locking up and causing your engine to die when it has high strain on it.