We're running 25 peak, 22 held on our 2wd with a T34, greens and a 4x4 intercooler. Assuming your injectors are up to the job (and the fuel pump and rewired), you should be able to put a little more boost through seeing that you have an RS500 intercooler.

I asked Mark (MAD) to set it up on the safe side, was done in July on a hot day and we were getting early signs of det with a touch more boost than that so he wound the boost down, and a little more

Make sure you get someone in the know to set it up for you as you want it