2007 outlander sputtering on full throttle

Hi I have a 2007 outlander 800 with about 5700kms. Bike works a1 until it gets down a bit in gas. After it gets down a bit if I nail the throttle it will sputter take off, sputter take off it keeps doing it. Sometimes if I shut the bike off for a min or 2 it will work fine again, when trail riding never has a problem runs perfect. I just bought the bike, when I got it home it had a bit of water in the oil. I pulled the tank today thinking it might have water in it, pulled the fuel pump assembly out and the filter on the pump was pretty dirty. Cleaned it up and cleaned out tank which was fairly clean. What is the chances that the dirty filter on the pump was my problem??
I was thinking of changing the pump but local automotive stores want $200 bucks for one. Hate to put it back together then find out I got tear it apart again and put a new pump in it. Whats everyone's thoughts?