Loss of acceleration

[tbagnall]

So I don't have the greatest knowledge of my bike yet, however since I've changed out my spark plugs due to constant stalling at lights (fixed that problem) it's been at a lack of performance. The throttle feels a lot less sensitive with an occasional hesitation and when I open it up it definitely isn't putting out 1125 cc worth of power. The bike is a 2008 1125r with about 2500 miles on it and idles at 1500 rpm give or take some. I have read up on spark plug problems and it sounds like that could potentially be the issue except that I changed them out 9 months ago. If anyone has any idea or needs a little more info to help please lemme know. Any thoughts are welcome and appreciated.