The torque converter still not locking up.
I did the following:
1. Changed tranny fluid and filter.
2. Replaced ground (negative) and positive battery cables with new 1GA cables with soldered on copper terminals. I wanted to upgrade the factory cables anyway as they appear to be something less than 4GA and were showing their age.
3. Added 4 new ground cables: engine-to-firewall, engine-to-right fender, battery-to-radiator support, transmission-to-body.
4. All ground surfaces were sanded down to bare metal for proper connection.
5. The infamous wire connection: 4-into-2, was soldered and re-taped (BTW it was in pristine condition, not even a hint of corrosion!).
6. All transmission connections/connectors and related sensor connections were separated, cleaned with electrical contact cleaner and re-connected.

Is there anything else I can do or check/test before I fork over more dough for another TPS?