Lurching problem and I'm out of ideas.

One thought other than the rear end:
You have an A999 (32RH)- Lockup convertor.
On deceleration, the convertor is not coming fully out of lockup mode; possibly locking/unlocking as you slow down causing your "lurching" feeling.
Reasons:
It only happens when hot, after an hour or so.
It happens on decel, disappears if put in neutral, if you accelerate or when brakes are applied.
Not knowing how your trans was set up/installed, I can only speculate that either the TC is failing or your line pressure is possibly low- slight chance the TC lockout solenoid isn't functioning properly, too.
Easiest thing first: verify trans fluid level. Check it hot, on level ground, in NEUTRAL. Park will give you a false reading.
Just a quick guess.