Re: PCV Valve Fouling my plugs and Bad Idle Quality
Having additional cruise timing via vac adv would be a good idea.
However, current timing locked at 34* is adequate & would not be causing low speed misfire; most likely cause is leanness.
If you have a choke, try this: engine idling, close choke blade until engine note changes. Lock the choke blade in this position with some tie wire. Test drive car. If misfire is improved/gone, you are too lean on cruise.
Note: the fix is not increasing main jets/PV. The fix is to richen the idle cct because low speed cruise is on the idle cct via transfer slots.