I am wondering if the RB25det ecu will work on a RB20 with the RB25 MAF?
that is a negative, if i recall the 25 has totally different wiring then the 20, u will need to get ur 20 ecu chipped for the 25 maf, autodreram can do this for you 248-1556 talk to marvin say rob parsons sent you 
Its not my motor the problem is that he doesnt have the RB20 ecu hes only got the RB25 ecu.
No dice. The rb20 is totally different than the rb25. I know that the rb25 and z32 ecm’s are interchangeable, but your best bet is gonna be to just go and get an rb20 ecm and try to sell the rb25 one.