A month or so ago I got on it hard in 1st & 2nd and all of a sudden I had a misfire & a check engine light. Ran crappy for about a mile and then normal with light disappearing. DashHawk showed a misfire on #1 cyl. (front drivers side). Next day I floored it again thru 2 gears and had a minor stumble and again the same code but no check engine light. Pulled plug and it looked fine, but since it had been in for about 10K, I switched it out. No issues since. I think I had some carbon build up that caused this, as I hadn't been flooring it for long periods for months. Engine had stock tune and I was running Costco 93.
Way back, I ran 30K with Torrie's tunes using the original plugs (old #) including with W/M and never had a code till on day the insulator broke loose on #1 plug.
Based on my Lambda(decimal A/F) readings that I have logged when Torrie was experimenting with my tunes, both banks run pretty equal, and both have occasional fluctuations. Early on we saw Lambda's as high as .84, but later Torrie got them in the .78 - .80 with an infrequent one or 2 reading spike as high as .82.
If you continue to see a mis-fire, you may need to do a compression check on #3 cyl, and compare it to #1 & #5, all three on front and easy to get to.