[jamotech741]

Ok, thats a bit more difficult. There is no good way to test an ecu other that swapping it to another 04/05 750. Buying used electrical parts is a crap shoot. Other things to check, the ground strap to the back of the motor is tight and good connection, all vacuum lines, especially the atmospheric pressure sensor. I assume youve already checked that all your connectors go to the right spots, more importantly coil and fuel injector connectores as they are interchangable. What about coils, those are different between the two models and will definately give you problems being there are resistance differences. All depending if the resistance is higher or lower you can do no damage or fry your ecu.