Way back when we'd just clean the idle air bypass valve. There was a point when the car got over 100k miles where the shaft had pitting and couldn't be properly cleaned any more. Apparently this bypasses the need to clean that part.
1970 Mach 1 M code
1990 5.0 LX Limited Edition
I keep noticing the DOT puts up signs to honor my burnouts. That's nice of them.