OK, and boost is getting to the ALDA in the same range? 13 psi is fine. I believe the wastegate is not the problem. I reread you post and noted you had the turbo off, you would have seen lots of carbon build up on the flapper if it was bad.
Timing might be the issue. I throw in the towel after that.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!