Mine was unplugged and caused the cat to die
My solenoid was unplugged for years when in ID...brought back to CA it had to pass smog again. It failed three times while I was sorting out the years of incompetent out of state mechanics that had no idea of emission systems.
One of the main problems was the unplugged feedback solenoid and that caused the truck to run rich and ruin the cat....$$$ later and now all is fine.
The solenoids do work well, the trucks gets better mpg at higher altitudes than at sea level and will perform properly now all the way to 9000 feet.