I think the MAF fault needs investigating before going any further. It's either faulty or there's a wiring issue. You won't get full power with a bad MAF.
The actual boost is 1.3 bar, or a shade under 19psi. VW ECUs measure in absolute pressure, so you have to deduct 1 bar to get your gauge pressure.
It is indeed a little sluggish to hit the midrange targets for a K03. You might want to see if there's oil leaking out of the intercooler connections, which indicates a boost leak.