Loss Of Top End Power

I have a 2010 Arctic Cat 450 EFI , When it drives it seems to have some power but not full , the bike will only hit around 20 Mph , just seems as soon as you crack on it, it bogs out a bit and just wont push out and top end power , ive changed the plugs and got a new fliter , that seemed to help a tad but not to much , I was wondering if its in limp mode or some weird thing , any ideas and tips would help a lot , Thanks