Fuel question

[Maisie]

I run a 1985 1600 S series engine Maestro, which has the following problem:

It normally runs on LRP. For a few months, it's started on the 2nd turn over or so, but then stuttered to the point of almost stalling 2 or 3 times before it runs smoothly (but at quite a low idle). It's had no power to pull up hills or awya from a standing start. I was stuck for petrol to get home the other day, and found myself at a garage with no LRP, so I put in some unleaded, and it seemed to start and get going better, and seemed a lot more powerful and faster. I've just repeated the experiment with Optimax and it seems again quicker, but not as good as the unleaded. I'd like to keep it on LRP to keep the valve seats OK - does this fuel "experiment" tell me anything about how to go about tuning the car to make it run better on LRP? It is likely to be rich, lean, or what?