I'm happy and had to tell someone:
I have had my Nissan 40C "professionally" tuned a number of times over the last few years and it always retained a rough idle. If it idled very long, the engine would quit. Last weekend I replaced the "just as good" Autolite 4093 plugs with recommended NGK B7HS plugs gapped 0.040. Now It idles smooth and purrs like a kitten.
I suspect that this is the first thing that would have been done by a smarter person but I relied on the repair shop.
I have had my Nissan 40C "professionally" tuned a number of times over the last few years and it always retained a rough idle. If it idled very long, the engine would quit. Last weekend I replaced the "just as good" Autolite 4093 plugs with recommended NGK B7HS plugs gapped 0.040. Now It idles smooth and purrs like a kitten.
I suspect that this is the first thing that would have been done by a smarter person but I relied on the repair shop.