I ran 11psi in my RX (has the same MPFI EA82T your XT has) and this is what happend:
This is with an intercooler installed, and a Bypass Valve installed running 11psi.
I rebuilt that engine using the block from a Non-Turbo SPFI EA82 which increases the compression ratio. I then left the turbo at stock 7psi and kept my same Intercooler & Bypass Valve.
The rebuilt engine with SPFI block and 7psi was much quicker than the stock EA82T block and 11psi. Your ECU wont let you go much higher than 11psi without cutting the fuel, so if you are looking for 20+ PSI you are working with the wrong engine.
With that being said, listen to Gen Disorder, he may sound like he's harping on you but he sounds like this to everybody... even his friends. We know what we're talking about when we say "dont waste your time or money, you'll regret it later"
Have fun with your XT.
-Brian