TBH if its coughing & spluttering the afr's will go all over the place.
So you need to start eliminating things that could cause poor or no spark.
Check for rotor arm condition
Check no moisture is in the dissy cap (is the o ring in good nick)
Remove the sprak plugs and check the colour
make sure all the leads are plugged on nice and tight to the spark plugs (if not squeeze them a little with pliers) You can also take a resistance reading to ensure they are within tolerance, very easy to do with a multi meter
http://www.youtube.com/watch?v=DI_aI8KElrM
Make sure your spark plug gaps are correct
Check the voltage at the AEI
Check your tappet clearences
Check that there are no exhaust leaks before & after the lambda sensor & where it screws in.
Check you have no air leaks on the inlet manifold/carb (buy a can of easy start and have a spray around, carb base, carb,inlet manifold).