[Jac Mac]

Vac advance on comes into effect at cruise/part throttle mode, however if its hooked up to wrong port on carb it may be getting full advance at idle & if your $400.00 mechanic did not realise this and set advance at idle with it connected your car will not be getting full advance on the road under power. Disconnect & plug advance tube then check ignition timing at idle ~10°/12° should get you started, then run up to ~2500+ and check your getting something like 30°/35° total advance to check dizzy mech advance for starters.