Guys, one other thing to take into consideration. I read an article a while back about some guys that were trying to dyno a car (I can't remember if it was a 'Benz or a BMW) and they were having trouble getting full engine output because there was a sensor that measured the amount of ram air hitting the front of the car. Basically the car knew that it was being run on a dyno rather then being driven on the open road and cut back the power, supposedly to reduce cooling requirements.

I don't know if our cars have this or not, but since you all are tearing into the ECU programming, it might be worth having a look.