on the early 92-96 ecu's whats the difference between a blue labelled z4 and a black labelled z4 and so forth?

 

Guess mine is black then??



Dunno about any difference.

 

Is there actually a blue labelled Z4?

The early ECUs have compatible pinouts. So they are interchangeable. The difference will be with the maps on them which will mean that they will have different ignition maps, boost limits etc.