Seon,
It sounds like your vacuum advance is working just the way it was designed to. You know what you are doing so finding the problem shouldn't be horrible.
Valves that are gummy and sluggish from a long nap could be a contributing factor to your miss.
The task at hand is to determine if the miss is being caused by carburetor issues, or ignition problems.
Is the miss a occasional miss or is the engine totally crapping out. If it isn't backfiring through the carburetor, can you slowly choke the air horn with your hand as you bring it up in RPM and see if the extra fuel brings it out of its spasm.
This will tell you it goes lean off idle and might be a float setting issue.
Bring the RPM up very slowly and see where you get into the 'crappy' area.. is it mid throttle or pushing full throttle.
What happens when you road test it under load, does it act differently, or is this not possible running as it is.
I would set the timing back to the factory marks for now. You can always tweek it later.
Stuart
