Whats the maximum boost that can be expected from a T38 and whats the max that it can be run at?

Was working on a cossie today with a t38 but I cant get the boost pressure above 20psi even with the actuator pipe disconnected.
Theres no air leaks, and the actuator is definetley holding shut.

Relevant engine spec is;
turbo technics t38
92.5mm bore
7.2:1 CR
BD14 cams
swedish inlet manifold
rs500 intercooler
2wd exhaust manifold

Anyone got any ideas to why i cant get any more boost pressure.
Is there any chance that the wastgate flap inside the turbo isnt closing fully?