OK, sorry about that I grabbed the wrong service manual, go ahead and grab a bottle of that anyway and run it through the engine. I'm not a advocate for additives but that additive works, what works well about it, is the efficiency to dissolve stale fuel, so if you have any of that going on it can have an effect on that also.
Next and this one I use as a maintenance on all my road bikes that are injected. Local autoparts store (O'Reillys), Chevron makes the BEST injector cleaner called Techron, Yamaha at one point marketed it under their name called "Ring Free" not only is it great on the fuel system but also will de-carbonize your engine and keeps the piston rings from build up.
The fuel injection systems are more forgiving and really require less maintenance then the carbureted models, however with fuel having a shorter shelf life and it gets worse its seems every year, its become more prevalent as we speak.
So I would try my two suggestions first and go from there, after you run these additives through and notice a difference, it wouldn't be a bad Idea at that time to go ahead and change the spark plugs to a fresh set.