DT, first off welcome, this is one of my favorite forums. I disagree with your diagnosis nothing more. MAP sensor or MAP temp Circuit, the terminology is not the point, the question was what’s wrong with the vehicle. I see them as related until proven otherwise, saves in part cost.

I will stand by my claim that the O2 voltage is the first thing to correct, voltage fluctuation with the manifold pressure sensor or circuit however you would like to refer to it is not IMO the cause it’s a result. If the MAP fault continues after the correction of the O2 voltage then I think MAF, MAP and TPS function should be checked (and vacuum leaks or course) . You state you need a BMW specific tool to check the O2 voltage I have been checking them will standard OBD ll Monitors/Scanners for years and standard volt meters before that.

As for P1620 code definition screenshot... I have similar reference maternal and I check it prior to each post, I know the what the text says.

ALL BMW’s use manifold absolute pressure data, we can talk about what verbage is appropriate but I’ll just stipulate the OBD ll text is correct and my terminology was less than accurate. Since BMW uses several different means to gather the data I used a general term MAP sensor to refer to the system that measures intake pressure.

I do have a question maybe you can answer, what does the DISA Valve or Adjuster unit as BMW calls it do? Part number on the unit I have for a 2.5 is 11 61 7 502 269.
Thanks