hey gram,, i just read this article in my BMW car magazine.
"ive got a problem with my 320d-it has poor acceleration and it feels as if something is holding it back when accelerating thru the gears.Ive had the airflow meter replaced but it has not cured the problem,,,any suggestions" and the answer that came back was...
"The airflow meters on the 320d are a common problem and just getting them replaced is not enough.Highams Park Motor Company 020 85233443 told us that what should have been doen at the same time was an ECU remap." etc etc
not sure if it helps,,but it just gives you an idea ....
maybe you gotta sort t out at the same time
i know they run in limp mode when there is a problem
my own car ran like crap,,,till i started to boot it everywhere,,,now the computer has detected my driving style and adjusted accordingly
hope it helps