I have been playing around quite a bit with my 04 STi/UTEC, and I can't seem to hit target boost higher than 16-17 psi, regardless of the CLB values (which I have varied as much as +50, as high as 430), and regardless of the ABC setting.
When I screw in the ABC to close it off, and open it a turn or two, I run 12-13 psi. But I can unscrew it until the top of the set screw is coming out of the ABC body (10-15 turns??), and I still only see 16-17 psi max (except for boost spiking).
I have checked the install repeatedly, and all the lines appear correct, no leaks as far as I can tell. The only thing that has me a bit confused is the "brass restrictor" that is supposed to be in the compressor side line of the factory T-fitting hosing. I just had my stock turbo replaced with another stock turbo (straight from Subaru), and it came with all the vacuum lines installed. The stock vacuum lines DID NOT have any restrictor in the compressor side of the T-fitting (nor anywhere else). I am familiar with the factory restrictors, having experimented with the 3/16 replacement on my 02 WRX years ago. But this factory setup does not contain a restrictor.