Fasteddie, Crankcase pressure is assumed equal to atmospheric pressure, nominally 15psi. Sure, the deeper you look it's more complicated as panic suggests but the basic assumption is valid.
PCV won't change the situation much because it is a mixture of air and fumes but EGR (exhaust gas recirculation) will because it's inert (composition nitrogen and combustion products). Including inert exhaust gas with the fresh charge increases the inlet manifold pressure and reduces pumping loss. There are some other benefits to EGR as well. It's not a bad thing, contrary to popular belief. EGR increases mixture motion in the combustion chamber because there is more of it and provides heat for vaporization. On the negative side EGR reduces peak temperatures which reduces nitrogen oxides which is the reason for EGR. Properly functioning EGR will help fuel economy and won't hurt power because at WOT EGR shuts off.
