KFX700 sputters/sluggish at speed

I started having problems with my 07 KFX700 today. Other than the Uni air filter, it is completely stock. It does not smoke, the air filter is clean and not over oiled, and spark plugs are fairly recent. As stated, it had been running perfectly fine before today. Anyway, it starts up easily and idles fine. The problem is that it cuts out and sputters when getting on the throttle and runs sluggish. It does get up to speed, but it doesn't do so smoothly. The valves are within specifications and I have disassemble the carbs and they were spotless. I still cleaned everything out with carb cleaner and compressed air, and replaced the jet with oem parts (stock sizes). I have also drained the tank thinking that there might be water in it. It was also very clean...no debris or water. Thanks in advance for any help in trouble shooting.

As embarrassing as this is to admit, if one person can learn from my mistake, it will have been worth it. After installing the new fuel pump, the original problem remained. Well several months ago, I had fashioned a pre-filter (out of pre-filter material) and placed it over the air intake that comes out of the air box. Since my wife never rides wide open, she never noticed the problem. It was not until the 4th time out, after doing this mod, that I rode the quad and noticed the sputtering. After testing the quad with the new fuel pump, I turned around to head home. I was riding without the cosmetic air box cover and looking at the screen covering the intake and I thought to myself, "self, there is no @$@#%$ way that the material over the intake could be causing this problem." I had nothing to lose, so I took it off. Guess what? The quad ran like a charm. So, after approximately 3 hours of labor and $50 later, I accept the dumbass award for the month. I guess it wasn't a total loss. I now know how to rebuild the carbs, I adjusted the valves, and gave it a tune up.

I know this post is old nacho, But i thought i would throw this to you. Most people on the kfx 700 do the 12 hole mod to the air box, all it cost is the price of a few main jets & around 1.5 hrs time to complete, the bike runs smoother & lets the carbs breathe better & u gain a few ponies in the process. If u need the how to the on the mod let me know.