TCC locking up at 74MPH at W.O.T

[Fast355]

Does anyone know what parameter would be letting the TCC lock at 74MPH while at W.O.T?
I've just been doing some W.O.T test runs in my van and noticed that the TCC is locking on once I reach 74MPH and stays locked until I lift off.

It's a 1993 4L60E running an $OD bin, 8625 PCM in a modified G20 van.

There are WOT or Kickdown mode TCC lockup settings in the ECM. From my experience it helps to lock the TCC slightly above peak torque and drag the engine back down to peak torque again. Keeps your engine in its powerband longer and creates more HP to the wheels.