How did you check when the wastegate opens? Is 11 psi the max you see on the gauge or did you apply a pressure source to the wastegate line? If you're reading the gauge, use a MityVac or some such device with a boost gauge tee'd in and see at what pressure the actuator starts to push the wastegate open and at what pressure it's all the way open.

That's good information but I'm not sure what to do with it As long as you confirm the wastegate is fully closed when there's no pressure signal to the actuator, you should be good. Then fit a ball-and-spring type manual boost controller between the compressor fitting and the wastegate actuator. Set it so you get 13psi at WOT in second or third geat at 4000 rpm. No need to adjust the wastegate.

If you want to adjust the wastegate, in most cases the rod between the actuator and the wastegate bellcrank can be adjusted for length. I think shortening the rod tightens the spring inside the actuator requiring more boost to move the rod.

Sixto
93 300SD