Yup, I do plan on passing through Denver.
A couple thoughts/data points I had today whilst riding:
--The engine oil is probably overfilled by a bit. I used the dipstick while cold, it looked too low, so I added some. Measuring warm, it's on the high side. I can see oil coming out near the airbox on both sides, dirtying my block and dripping on my boot.
--It doesn't happen at 55mph, but 60+ it does
--I tried hitting the kill switch briefly while on the road. The slowdown from just turning off the ignition is much smoother than the problem I'm trying to diagnose. This makes me think it's something that's causing an imbalance (i.e., it's only happening on one cylinder). The sound is very different, too.
--I adjusted the valve clearances today, to 0.010 exhaust, 0.006 intake. Left cylinder was already at those settings, right was at .008 exhaust, .006 intake.
I'm going to measure coil resistance and perhaps remove a little oil tomorrow.