I did gap the plugs today and they all measured fine. But, #2 is slightly sooty. The rest looked perfect (no soot, no oil, no white spots, just brown/grey)
@awfulwaffle: huh, alright. That's easy. I'll try swapping #2 and #4, and see if the problem follows. I'd never heard of that before. But it seems to match. Had no codes the first 300 miles, and then intermittent since. Thanks.
@mikeofree, yeah, I've been thinking about that, but didn't want to drop the money for no effect. Guess I'll try that if the misfire doesn't follow the plug. Still easier than trying to gap valve clearances.
I was pretty damn picky about the valve lash too. I triple checked every valve and torque spec cuz I didn't want deal with any internals once the engine was in the car