This is called a shift flare, and if the fluid level is correct, and the bands are adjusted right,then the cause started with either faulty lipseals or a hung governor.
All your dicking around with the KD, which is actually adjusting the throttle pressure, is pointing to the governor being ok, and testifies to leaking lipseals.
A pressure test will reveal the problem.
But honestly, it's only a lil more work to take the trans down and look it thru.
