I've been hunting down an underboost code for about a month now. Checked wastegate linkage and found no play. Smoked the system multiple times and have found no leaks anywhere. Replaced PCV due to check valve not sealing. Was chasing a p0172 rich code for a while until I found the purge valve was leaking vacuum and the rich code seems to mostly have gone away from returning daily to one time in the past 3 weeks. I'm just about out of ideas and without being able to reach the CHRA on the intake side I have no idea. Ran some logs and found that boost pressure is incredibly spikey which you can feel under WOT. Replaced boost control solenoid, Diverter valve, and intake manifold as well recently.