05 sportsman 700 efi running erratic

alright fellas. I’m stumped. I’ve had my 05 sportsman 700 efi for quite a few years now but lately she would run good for 5 to 15 minutes then out of nowhere she starts spitting and sputtering unless I’m full or almost full throttle then She seems to run like it should until I got back to like say 1/4 throttle. It can’t be fuel pump issue cause it does run good with the throttle wide open. So fuel delivery is meeting that demand. Any help?

 

Just a guess but maybe the fuel pump is not getting a strong enough pulse signal at lower rpm? Also if your battery is low or stator not putting out enough voltage at lower rpm that could cause a week spark. Check voltage regulator also.