Could be a soft spring. You've cranked the MBC all the way to full max, and it wont' go above 19 on your gauge?

 

turn the boost controller up for petes sake!!!

 

Your stock solenoid isnt still hooked up is it?

 

if you dont want boost taper upgrade your wastegate acuator or get a external wastgate.

boost controllers dont make a big difference unless you get a hallman pro RX or something of that nature, even with that i still have a little taper. but the hallman made a huge difference. i love it