I bought the bike used 2 months ago currently with 18k miles. It makes a sputtering noise and hesitates at the same time between 4-8k rpms but between those it gradually climbs then rides out like normal. I dont know too much about the bikes history, only that it's been dropped on the left side with the stator cover damaged, but replaced with a new cover and stator. Right now I'm just checking the basic stuff before I start throwing huge money to get it done by a mechanic. Before it had a stock set up with a stock exhaust but had a k&n air filter but that was about it. I got rid of the stock can and replaced it with a Tbr exhaust. Keep in mind that it still had the problem even before replacing it with a slip on. What I did was check the spark plugs and looked and smelled like it had gas on it (a little wet) checked the fuel pump and replaced filter, changed oil along with filter, checked air filter, checked/adjusted clutch cable, throttle bodies, and coils. All in good shape. My last thing to do was to get a PCV hope the sputtering issue goes away, but I needed one anyways since the aftermarket air intake and exhaust were added. I also think it may be bad TPS or clogged injector(s), but I'm no professional. What info can you guys provide? Help is appreciated.