Variable idle and occasional jolting miss

[Nikkum]

1985 FI. I thought my lovelly car was now perfect. Set timing at 10. Valve gaps perfect. Plug gaps spot on. Drives fantastic . Good power .best car I've ever driven.
Problem is occasional backfire on starting and fluctuant but smooth idle at around 7 to 800 when cold and really annoying jolting misses . Rare and random.
Where should I start? Is this likely to be timing and should I vacuum gauge it? Could it be air leak in fuel supply? Vacuum leak?
I'm checking everything but does anyone recognise this as a particular problem?
V grateful for pointers!
Nick

[RRoller123]

Check connections at the injectors. Have they ever been sent out for cleaning and service? Check the connection at the AFM, and make sure the door swings smoothly without binding. I had the same thing happen last year and it turned out to be a loose spark plug wire. They are easy to check too.