Type 3 MPS Sensor

US Delivered '76 Jaguar XJ12C.   I recently had the injectors cleaned and flow tested.  New injector harness and engine harness.  All wiring in excellent condition with full communication with the ECU.
My MPS, Type 3, has had the 4mm hex screw turned prior to my ownership, I know because I was told by the previous owner.
I've read this wonderful D-Jectronic website on the MPS but don't quite understand what really happens when turning this only adjustment screw of the Type 3 clockwise or counter-clockwise.
I'm not sure how to adjust the MPS to get it back into acceptable range for the engine.?
Currently, the engine will cruise very smoothly at any rpm above 1,500.   Idle at 750-850 is rough.  I have turned the idle trim screw on the ECU a few notches CW and CCW trying to find a smoother idle.  It definitely changes the exhaust sound and I have it currently set with a "softer, lighter note with hot exhaust temperature."
But wondering how to calibrate or to tune the MPS?
One symptom I think I have:  When giving heavy throttle, but not WOT where the throttle trigger board signals to the ECU I want full power, I feel the car is pulling as it should, meaning under powered.   (Timing is correct).  So I think my MPS needs adjustment.  (Yes, it passes the ohms test and vacuum hold test)

Thoughts?

thanks, Charles in Dallas, TX

Hi Charles,

if you were in Germany, I would now offer out of curiosity to take your MAP sensor and adjust it. But I am afraid that this seems impossible with Dallas. What you can try as a try to come closer to correct setting is that you use a lambda braodband sensor and drive at let's say 2500 rpm gliding and then try to adjust to Lambda 1. That is nothing precise but approximation.

It would be better to send to Bosch Classic koller.de at Nuremberg.

Thank you for your answer and suggestions.