I am working in a buddy's 02 Sportsman 700 and it runs like crap past 3/4 throttle. It spits and sputters until I pull out the choke. I can pull out the choke slightly and the it will clear up and run fine. It sounds like a vacuum leak or a fuel starvation issue but I think I have checked everything. I have cleaned the carb from top to bottom and replace the all jets, new plugs, new rubber intake boot, new air filter, fresh non-ethanol gas, and replaced the fuel filter. Float height set at 14mm and jet needle on 3rd notch and running a 157 main jet. Im at about 1000 ft elevation. The engine is healthy and has plenty power. I've done all I know to do. Any help would be greatly appreciated.

there was a recall for the crankcase breather that goes from the valve cover to the airbox, if it has the big plastic filter on it, then it needs replaced, dealer should just give it to you

It may be carb related OR could be the Ducati ignition going south if it hasn't been replaced with the updated Kokusan ignition kit. Wasn't a recall (should have been) but they ALL will go out, some sooner than others. 2002 to early 2004 carb models were affected! Check all the posts on 700 ignition problems. One of the symptoms is cutting out,spitting back,loss of power. Some owners have just killed their atv and wouldn't start back up!
OPT

Can the breather filter have an effect on how the quad runs?
Would it be safe to remove the filter and see if there is a difference?

Think it was just a bulletin for the inner diaphragm or cover? Too long ago to remember,but shouldn't affect it that much,just kinda made an oily mess around the valve cover. You can remove and try. OPT

made my 03-700 run like crap, when the breather filter cracked, there is a recall on these aqnd dealer will give you a new breather line without a filter

Check the boot between the carb and the motor. These are famous for cracking on the underside of them.