Thats a little over simplified, after all, what would be the manifold pressure on that 2.0 16v at 150bhp? I would wager minus a couple of psi at least.
Otherwise how could throttle bodies improve anything?

So looking at absolute pressure, you are talking 12-13 psi probably, so at 29psi (1 bar of boost) its easily possible to put more than double in, as you have effectively got about 2.3 times the pressure differential

Then when you consider that the engine wont get below a couple of psi at BDC anyway as it didnt empty its cylinder totally, you realise you are actually not talking about 12psi differential, but 10, and your 29 represents 27, so nearly 3 times the amount.

Then consider that was all at BDC, and most of the cycle the piston isnt, and you will see even more difference!


See what I mean about over simplifying it?