So I got a set of Champion double platinum plugs (delivered to my door by O'reillys for about $50). Gapped them at .045 and installed them. According to my notes the old copper Champions had been in there since 2015. They looked pretty good, but erosion of the electrode had opened up the gap to .055 to .060. Its was time for them to be changed. With the new plugs in, I cranked it up and it ran significantly more smoothly. Hopefully these will be trouble free for a long time.