26psi isnt even 2 bar i think you need to be upping the boost to 2.2BAR and then seeing what power you making

2.2Bar = 32psi

if you want to run more power with only 1.5BAR of boost i sugest changing your inlet for a small turbo one or better and putting a bigger turbo on getting better cams and having the head ported to suit

i would personaly run it at, at least 2 bar and see how you get on most of the engine builders here in the UK run there engines on 2.2Bar to get there figuers