Please HELP!!!!!!!!!!!!

Ok here the thing my ds650 is cutting out around mid throttle range really bad and al little at top end. I thought i had problem fix by taking off the lid to air box but today was the first day of really taking it out on the trails and i figured out that wasn't my problem because it was doing it a little while after running it and it got progresively worse through the ride even though i could get it up over 70mph no problem. So along the way home i took out the needle and moved it to the fourth slot from the top put it all back together and took off it ran fine no cutting out at all ran really smooth. Except it was lacking a ton of power i couldn't even get the front tires off the ground. But i still could get it up to around 50 mph just took me awhile instead of being a 650 it seemed like a good running 90cc.
So my question is what am i doing wrong in the carb because that has to be the problem.
I have Dyno jet kit main jet 175 and k&n Filter thats it for mods