Near the end of the war with the availability of 150 octane gas, they were looking to run the Griffon engine Spirfires up from the common 18 lb boost to 21 lb, which boosted the engines power from 2,000hp to 2,200hp, so I am wondering if I change the manifold pressure value from 67" to 80" to reflect 21 lbs, is the engine modeling such that it will actaully produce the 2,200hp figure, assuming there are no other real life engine variables changed in that equation?

Probably better to do so using the enhanced Water Injection modelling in the FSX flight model. But Rob Young would be much better placed to provide an answer. You could easily upset the engine settings with such a `simple` change, but it might work.Allcott