Hi all
The checks are called out in the maintenance manuals line, MML, for the check of the connectors every 200 hours. You need to be at least 30 NM, 7 lb force, or the spark plug or connector must be changed. If the wear is on the spark plug thread then you need new plugs. If you have low reading with new plugs you then need to replace the connector.
Given both the "old" NGK end and the new version PVL brand have exactly the same value resistor internally I see no reason you could not mix them on an engine. I would not do that with the spark plugs themselves but the connectors are not an issue. Both are rated at 5K ohm resistance.
Cheers