Was that 2lbs of boost at WOT? My bet is that it is NOT the turbo itself but something else...

Other questions

• Fuel Filters (tank screen, primary and secondary)
• Air Filters
• Injectors
• Timing
• Smoke?

It is possible that the PO figured that the switchover valve was bad and bypassed it. Have you tried removing/adjusting the alda?

I am sure the question of valve adjustment will come up as well. When you have it floored are the linkages pulling the IP to the stop?