I think the high idle is probably an indication the OVP is functional. The engine control module is adjusting idle speed to compensate for over-enrichment. Removing the OVP or its fuse could verify that. Mixture is probably set rich to allow it to start at all when cold.

Could be the EHA is shorted, and was disconnected instead of replaced. Still, all items can and should be tested, replaced as necessary, before diagnosis can continue. The EHA plug appears to be missing in the photo, but it is hard to believe it was cut off unless the wires fried. Maybe it is twisted back and hidden at the moment. In our 190E, it runs from the harness that lies right parallel and next to the cam cover.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7