check the black rubber elbow pipe from the inlet manifold to the brake servo ! these collapse and split ( normally on the underside ) just of the end of the inlet manifold.

2nd check the throttle body mounting plate ! large rubber block, these split and allow vasts amount of air in! one way of testing is when its ticking over try and lift the carb/throttle body ie tilt to left and right ! if it stalls or splutters it needs a new mount!

The carbs are normally mounted on a rubber block and the block starts to split causing kangaroo effect on light throttle ! The elbow hose to the brake servo pipe , ensure its sound on the underside ! normally the fuel lays on the inside of ot and rots the bottom out so when you look at it it looks fine !

I would check for air leaks like vacum pipes etc if the problem is more on light throttle.

If it was ignition it would be under load, unless you have a fault with the distributor and the vacum advance is causing a problem. You could try driving with the vacum advance pipe of the distributor to see if that stops the problem !