As a background, I've been having a "ghost in the machine" on and off with my motorcycle for a few years. It'll start idling more roughly, run hotter than usual, give less power than usual, and have these significant non-linear jumps in engine noise / effort at around 7k RPM.
I bought the bike at a shop that has since closed, and for a long time it was under warranty. One time I brought it in, and they replaced some jet seals (or something like that), because it was a common issue with the model (2007 Yamaha YZF600R). It seemed to get better, and then came back. Brought it in again, and they cleaned the carbs, changed the fuel, and things got better. And then it came back. They started blaming old / crappy fuel, but I ride the bike at least a few times per week. I tried switching to fancy gas for a while (Shell / 76 instead of AM PM), and it still came back.
Anyways, it came back again a few months ago. With the shop closed, I was about to look into cleaning the carbs on my own. Sea Foam has a great reputation, so I thought I'd try that first.
I had about one gallon left in the tank, so I put an ounce or two in and flogged the bike on the back roads a few days ago. I noticed an immediate improvement after that ride. I finished that tank, put in another 4 ounces during a fill (it's a 4 gallon tank), and it's continuing to get better. I haven't even needed to do the direct injection / smoke fest treatment - just a simple gas additive.
It's nice to have a healthy bike again - and for only $10 of Sea Foam from O'Reilly Auto Parts!