Newbie B11 3.5 Question

[CrisJ]

Hi! I am a newbie in this. I am the proud owner of a B11 3.5 (1988 E32) and the tachometer does not work. It used to work with the original ECU but I had it changed to a regular BMW (swapped over the Alpina chip) since we cannot make the original ECU idle properly. Is the original Alpina ECU different from the regular BMW? If not, is there a way I can modify a regular BMW ECU to work in my Alpina? Any help/comment would be much appreciated.