Nice write up.
The same ECM connector B has a ground wire that I use for the FAS system. It is pin 20, A brown/black wire.
The taped ground will probably work for a while until humidity causes the copper and steel to corrode, so when you get a chance, you may want to move the ground.
Photo showing the location:
http://www.99mpg.com/mima/pininstall...ctionsr1.jpg,0