Well, I haven't had the pleasure of getting under the skirt of an FD but from what I have read it is the most precision piece of the CIS puzzle. The center plunger/bore has some very tight clearances. There are also rubber o-ring seals on the plunger. Yours is from a 73 ..making it 34 years old. I can't imagine that its working at spec. That said, I think anyone that plans on keeping the CIS system on their car for another 30 years might think seriously about having a nice rebuilt spare on the shelf.
If you are running rich during your break in period I would guess the rings will have a difficult time seating.

I've also wondered about the modern blends of crap they call "gasoline" now having a deteriorating effect on components, particularly internally where you can't necessarily see it.

Many have said that increased levels of ethanol in fuel (ie beyond 10%) will result in increased deterioration of CIS components.