Everything is stock, about 47K miles on the clock. I ride nearly daily (commuting to work) year-round.
A few days ago leaving work, I noticed that it would not accelerate. Idled fine, even running the throttle up in neutral, but once in gear it just completely lacked power, although if I accelerated slowly, I could nurse it up to speed. If I rode it below about 2K RPM it seemed fine.
Thought maybe the petcock wasn't fully on, so worked it back and forth, the problem went away after a few minutes.
This happened a couple more times on different rides. Starting to doubt petcock issues (I feel the detents clicking in as I rotate the selector, albeit maybe a bit sticky).
Added a gallon of gas with a couple ounces of B12 Chemtool (tank pretty low, maybe a couple gallons before I added), and let it idle 5 minutes before shutting down that evening prior to next ride.
This morning it didn't start like normal (died once after starting, didn't sound 100% healthy). Restarted, let it warm up. But as soon as I hit the street it really acted bad. Falters very badly when attempting acceleration. Decided to turn around and drive the truck to work.

I always refuel from my gas cans, which I always treat with seafoam (1 oz/gal).
Will have to wait for weekend to begin troubleshooting. My initial thoughts are to pull the tank, check and possibly replace vacuum lines (since I've owned it aprx 3 years, haven't ever looked under the tank...) , give the petcock a thorough testing (can it be lubed? It does seem a little "sticky" at times).
Appreciate your thoughts!