Fuel Delivery Problem
 

I recently had the local Valvoline place hook my 2000 4cyl. Protege to a OBDII to find out what my check engine light is for, and they said the code was for a lean condition. You can't really tell while driving, though to me it seems to be a bit more lethargic at the low end then I am used to. And every once in a blue moon it will shudder for an instant at a stop, like it wants to shut off.

Are there any known issues I can check myself to see if they are the problem, or should I just take it to a dealer? I already ran through some fuel system cleaner just to be sure it wasn't simple blockage in the lines.

did you try doing a proper tune up??? I.E. plugs, wires, cap, rotor(if it has them), PCV valve, fuel filter? if that doesnt help start looking for vaccum leaks....like hoses, intake manifold gaskets, anything like that...lemme know how it goes.