Hi Ilengine,
I can only report matters as found. It is interesting that Briggs specify resistor plugs across their range of engines as does Dempsey in his book about repairing Briggs engines. If you've never used one just wonder what service you've been giving your customers.
Just out of interest I bought a new NGK B2LM plug this morning and tried it. My engine started to backfire within a minute of starting up. Back to the BR2LM and it ran perfectly again.
At the end of the day I suppose it's up to the reader to decide whether to use standard or non- standard plugs.