I removed the 10cm harness bolt and the two 10cm stud nuts, along with the plastic cover that fits over everything. The ECM won't budge. I can wiggle it a bit, but the studs are moving with it. The ECM casing looks like aluminum, so I don't think it's rusted in place, but it sure acts like it. It does look pretty crusty (what little I'm able to see). I shot some WD40 around the edges and in the stud holes and let it sit overnight. I'm not seeing any improvement today.
Is this common? It definitely sucks. Pic attached.

 

I am not familiar with that gold piece to the left of the bolt hole but it looks like it could be the issue. You might try tapping on the studs to see if it releases.

 

^^^ What he said......I would say that piece is a tab that holds it in place.......try pushing it over with a screwdriver and see if it frees up.......Possibly one on the other side?????