I thought that was for a 2wd loom STU?

All 4x4 saph looms i've had the earth is attached via a bolt that fixes the 2 parts of the plenum chamber together but not at the throttle cable hanger its further back toward the bulk head behind the throttle body and to the back & bottom of the plenum (1 bolt back & bottom from the end of plenum if my memory serves me right)

I've always personally run an extra wire from the plenum to the negative side of the battery