From my experience the "updates" were the results of one too many cups of coffee being spilled into the shifter.
The shifter is also a control unit in its own right.
Up to mid 98 the .6 had a bushing style center support and light duty freewheels. Both would fail, the freewheels were upgraded to the M120 parts (along with a few other bits) and the input shaft center support was upgraded to a roller bearing setup. The valvebodys underwent many revisions as did the ETC.6 ecu's.