smash the teeth out of his head with a claw hammer then. they're only £1.99 in homebase. will be the best £2 you ever spent

or a not so serious answer to him is that yes there will still be 15 psi of boost, but that will have put in say 300g of air at a cold temperature, but only 275g at a hot temperature due to the difference in density.

on a n/a engine, you will be running at lower volumetric efficiency than a turbo one, so any change in density will have less of an effect (even ignoring the reduced performance of the i/c at high ambients on the turbo engine). a 10% reduction in density on a volume of 70% of 2 litres is much less than a 10% reduction in density on 100% of 2 litres