A washer at one of the tensioner attach points was accidentally installed under the tensioner instead of under the nut. Not one of the large centering washers discussed, but just a small 12mm nut washer. It being under the body of the tensioner was causing the it to rock out of alignment depending on which of the other tensioner bolts were tightened first.
At least I hope that was it. I still need to reinstall and test.
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90 300zx TT 13.285@106.08 (old stock turbo set up) 94 Camaro Z28 13.751@101.83 03 WRX 13.973@94.88 02 Mazda MPV; four kids and a wife don't fit in the Z. 90 240sx (sold) 16.9@87