There was a lively discussion going in the W02 thread regarding the consistency of the MB engines and suggestions that Mclaren and FI are not being given the prime engines, but rather MB is hanging onto them for themselves and further conjecture that this may be the reason behind W02 eating rear tires.
The suggestion is most likely false. As I have said before, any claim that top end bhp has anything to do with what a team is looking for in a motor is irrelevant. Each team is going to apply their own ignition map over the engine which meet their aerodynamic needs. An engine with 800bhp at one rpm but 650bhp at another may be great for Mclaren, but terrible for MB. I am 100% positive the teams are looking for different characteristics in the motor anyway. I would be more interested in knowing if FI or MB request a different camshaft style to Mclaren than peak bhp.
That being said, I have built and tested enough Ferrari street motors to know specifically what each one of them makes, and there is never more than a 2% difference on the top end when all things are the same. I have seen all of two Cosworth DFV motors on the dyno as well, and both were about as identical as one can get, and that is with 40 year old F1 technology.