1. Has the car been live mapped?
2. Has the cams been dialed in correctly?
3. What turbo and management?
4. What exhaust manifold and intake?

500bhp now is really the norm but back in the day it costed a lot 8 injectors T4 cams ported head etc etc.
I remember being at a rolling road in approx 2006 with a well known guy and he was trying to get the 500bhp, And was shocked at some of the other cars figures for lesser mods.
I said you need that live mapped and set up. Once that happened he had over 500bhp and now runs excess of 700bhp!!! Why because you always want more.

Paul