2004 gas ezgo starts off really slow, picks up on flat grade if I am on a hill or even flat at the bottom of a hill it will not Pull it. Engine continues to turn over but is really not running.

SOURCE: Misfire & power loss

maybe its time to replace your fuel injectors or fuel filter ?

SOURCE: engine will turn over but will not continue to run

the fuel filter is in the tank on top of petcock that bike has a vacum operated petcock(fuelvalve)if the vacum hose is bad no fuel flow check the back of the fuel valve for a small hose that goes to the manifold make sure it is good put vacum on the hose wile hooked to the fuel valve and make sure that gas runs out of the hose give me a rate please hope this helps

SOURCE: lack of power when climbing hills and slow to pick up speed

It sounds like your vehicle needs a major tune-up. Try putting in some fuel injector cleaner gas additive and a new air intake filter.

SOURCE: No power, idling rough

Replace the catalytic converter and EGR valve

SOURCE: won't pull itself up hill

You didn't indicate what model of tractor you have but most likely it is a hydrostatic drive problem . The power is transfered from the engine to the wheels by hydraulic pressure. If the fluid level (hydraulic oil) is low then it won't drive correctly. Follow the owners manual to check the fluid level. The other possibility is if this is an older unit it could actually have water in the oil.The water will not operate correctly. Where did the water come from? The transmission housing, is vented to atmosphere. On a hot humid day, while you're driving, the fluid and housing is heated. When the tractor cools, the ambient humid air enters the housing. When night rolls aroound the water condensing inside the housing. If you're lucky this transaxle may have a drain plug in the bottom. You can remove this and see if the oil looks milky. If it does, I'd drain it all and refill with fresh oil.