[HarryD]

I would bring it back to the shop that did the work, tell them want happened and what you tried. Hopefully they will make it right.

If you want to do it yourself. You need to be sure that:
1-Valves are properly adjusted
2-No vacuum leaks in the intake
3-Points gap is within spec.
4-Timing is dead on at 5000 rpm
5-Idle is on spec and not changing when fully warmed.

Then and only then do you mess with the mixture.

I have had my 1973.5 CIS car since 2001. The only time the mixture has been adjusted was when I first got it and it was surging, when my valve guides were replaced and when I had a full top end done.

I got it with 116k miles and it has 162k now. While CIs has it limitations, it makes for a wonderful touring car.