It sure sounds like the tranny thinks the engine is at WOT.
I'd try the adjustment again, maybe with a helper.
When my 86 needed adjusting, the mech had me hold it at WOT while he adjusted it.
96 T/A, Black/Graphite Leather, T-Tops, 6 speed, 10 speaker Delco/Bose "Monsoon"
Original owner, 194k miles and counting.
Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
Comp cams Xtreme Energy LT1 266HR-14 street cam and springs.
Custom leather interior at 190k miles. Total repaint 193k Miles