I’ve got a 172 that just doesn’t idle well below about 1200 rpm, I believe it’s running pretty rich. It’s not unsafe, I just know a O-320 with idle smoother. I know the throttle shaft has some play, do these usually tighten up with replacing just the bushings, or does the throttle shaft need to be replaced with the bushings? The idle mixture screw seems to back out after it runs for a few hours so I’ve ordered a new retaining spring for that as well. Thoughts?? Also, I haven’t been able to find a MA-4 parts diagram online, does one exist?