Glenmore, I assume your engine is a 104 with the CIS injection system?
I have looked for a similar problem on my '91 SE for only 18 years or so. I've checked and replaced every part on it, with the exception of the complete fuel distributor. Still looking.
It's not too bad, always starts and runs perfect on the 2nd try and a few seconds of chug-chug. But it's slowly getting worse.
The usual suspects are as mentioned; fuel pressure loss due to check valve, regulator, accumulater, injector. Weak ignition due to wires, plugs, dist, rotor, coil.

None of these, or a thousand other things, helped mine.
I'm still waiting for that "That's it" moment.

The things that had at least a little temporary improvement were the two sets of new injectors, and adjusting the EHA a bit richer.

I could write a book on the lack of success and theories I've tried.

DG