I questioned the PCV operation, mainly because the hose connecting R and L valve covers (back of motor) was kinked and unlikely to be flowing much. However:
1) PCV valve was definitely operational- checked for vacuum while engine was running and when disconnected the motor stalled.
2)There was some draw on the air inlet on the RH valve cover (not a wholelot though...)as judged by plugging the inlet with the prverbial thumb.

Also,in terms of IDing the guides as the issue, the springs on at least the RHS valve appear to have some slight discoloration/soot on their upper reaches. Ordinarily,I'd expect them to be spotless?

Paul