I just purchased an 03 zx6r and am having issues. Under 4000 rpm it coughs and sputters, you have to baby the throttle to get it to 4000, once you get past there it revs the rest of the way perfect and doesn't have any issues. (in neutral It isnt as hard to get it to rev as it is when you try to drive it) I have searched the forum and found some that are the opposite where it runs awesome on the bottom and then wont run up top they say anything from fuel pump to injectors to lines. I am wondering if it is a sensor, throttle position sensor or something simple. I pulled the tank and air box off, there are two sensors on the front of the throttle body, I am assuming pressure sensors because one is hooked to a vacuum line and the other is just open. Well at least that is how it is supposed to. Mine had 3 sensors, the one hooked up to the vacuum line was unplugged and another sensor was just lying by that one. If I hook the line up to the plugged in sensor the bike bogs down and dies. I have switched between all three sensors and it is the same. I have tried unpluging the upper butterflies and it doesnt change anything. I have done mechanic work on snowmobiles, four wheelers and dirtbikes. Just haven't delved into the street bike world too much. I am lost any help would be greatly appreciated.