I got around to replacing the ERG valve. The bolts are in very tight. I broke a 10 mm 1/4 inch drive socket. I had it a long time.

The trick is to use 10 mm box end wrench and to come in from the back to loosen the bottom bolt. If the wrench is too long, it won't fit.
After loosening the bottom and removing the top bolt, the erg valve rotates, exposing the bottom bolt. It just cleared the alternator.