Do you have a Renix Engine Monitor? If not check the resistance between A & B of the O2 sensor reading should be 5-7Ω. You can also check EGR function?
https://comancheclub.com/topic/73480-21-–-renix-egr-valve-test/#comment-769327
From the FSM is in this post.
https://comancheclub.com/topic/38225-egr-solenoid-renix/
There’s only one bolt which goes through the “cup” portion in the rear hole the other hole is for alignment of the bracket. They have a raised portion on the back.
I believe they were a factory/ dealer accessory. They are listed in the Mopar Accessories catalog dated September 1991. Apparently there were also stainless ones available.