maybe they are getting to that age now that everything starts failing or wearing? I'm sure they were very reliable when new.
i'm sure there are many SC's out there which would easily take 5k USD to get all their CIS components back to spec.
and it's not easy to DIY. You gotta be adament. It's a lot more difficult than just opening something up, cleaning it, and putting it back together (have fun with the FD!) . Spend days and weeks reading up on jetronic, studying like in school, geting hernia from working on the 3 million fuel lines and the unreachable rear AAR bolt, nevermind taking off the A/C and blower motor for the 20th time
so yeah, better be prepared.