Thanks for taking the time to do the maths Blackdog. I don't use the 'boost' because I have never really noticed any gains that are worth the risk of engine damage if you forget to disable it.
But I do look at the manifold pressure guage to check I haven't blown a gasket......
I have read Spit pilot accounts where they describe (in passing) enabling 'boost' or 'throttle through the gate' to get out of trouble and head for base.
If I fly straight and level - full throttle, with the boost cut out positioned for that extra bit of throttle movement - I don't see any increase in RPM, IAS, etc. That left me wondering what should I expect to read on my gauge at 18000ft for example and what performance gains I should expect to see or get.