im using a t3 wastegate on my td05-12b, when i get it on it at full throttle it starts building boost a little after 5k rpm, but it only goes up to about 4-5psi before redline...i checked for leaks in all the piping, so i thought the wastegate might be fucked and i used the hm boost controller (2 fitting, spring, bearing) and its pretty shut... still only goes up to about 4.. could the wastegate still be fucked or could it be something else?

 

I concur

 

the flap inside the turbo? it seemed closed, but ill double check it.