I have the same turbo setup but I turned it up a little past 19psi and detonated the hell out of my motor lol. Rebuilding the bottom end now at mazwork and sleeving the block.
Nice #'s! Do you happen to have a picture of the timing map from your power fc tune? Who tuned it? I am unsure if powerfc has the ability to control an electronic boost controller, but if it does, you can use a mac valve to help the turbo come online sooner. ( That's what I did, but I am on Megasquirt )
As far as your cam choice, why did you pick a 260 cam? I would think a higher lift/duration cam would suit this turbo better. I run jwt s4hl's on my setup, just curious if stepping down to a less aggressive cam will help with spool.
I also had the noticeable lag, but it only happens if I am in the incorrect gear. A simple downshift usually fixes it
Also that engine bay is super clean, nice build!