Thanks Anthony. That makes good sense. I had actually been thinking that my 30k service could have improved performance due to new plugs.
I have low comfort in the shop. I took it there because I thought having a history at that shop could help with 30k checkup/diagnosis (previous owner used them for about 10 years)... and I'm shopping for a service place. It's maybe a 6 bay outfit that's basically all MBZ. I looked it over when I dropped by for parts a couple of times.
So it looks okay... results to date are weak.