I'm recently purchased a zxr 250 that needs a little work. It seemed that it had some major airbox leaks which was causing it to get way too much air and starve it of fuel. I replaced the airbox and it made a huge improvement but still isn't quite right. It runs perfectly till about 9k rpm then stutters a bit till about 12k then kicks back in but still feels like it is about 25% down on power - tops out at round 165 clicks. The top of the carbs looks like it should have o-rings between that and the airbox - should it - I havn't got any but I tried some silicone gasket stuff with no noticable improvement. The other thing is looking at the online manual I saw a part in the airbox that I don't appear to have can anyone ID it I've posted a picture of this section of the manual. Only other thing I can think of is that vacuum valve thing that sits forward of the carbs. I think I've got all the hoses connected to it in the right places but its not that clear in the manual so I may have made a mistake. I've given the carbs a good cleanout and they appear to be in good working order so I dont think thats the problem