Bob: If nothing shows up in the numbers and you can rule out things like induction leaks, perhaps spend some time under the cowl looking for witness marks and interference.  When looking at the engine at rest, anticipate the engine moving forward, front end down and twisting counterclockwise (looking forward) about half inch to one inch in each of those motions.  Then look to see if anything might be interfering in that projected area.     An induction leak would tend to worsen in the climb as delta-p  increases and the temp is climbing from the turbo.  Going LOP would then make that cylinder or side of cylinders worse.    Those are my two thoughts on the issue so, based on armchair guesses, you are probably safe to rule them out!  Good luck.