Guarantee it's your wastegate actuator. Pop the e clip off, DON'T LOSE THIS CLIP IT TENDS TO SPRING OFF SO KEEO YOUR OPPOSITE HAND ON IT, break the 10mm locking nut. One turn at a time clockwise to tighten actuator arm. Put clip back on lock the nut. Go for a drive. If still not maybe one more turn. There's gotta be a certain amount of preload to keep the wastegate closed until target boost.
Then come back and tell me I'm right.