I have a 2007 cobalt ss/sc, gm stage 2, 2.5 cat-back exhaust. put my stock intake back on. When i give it gas under a load it sputters and throws a dtc, p0171, system lean. i do not lose boost and have no vacuum leaks ( checked by using carb cleaner ). ive replaced the fual filter, maf senmsor, injector sleeves and o rings, clened throttle body, used injector cleaner. Tried about everything i could think of. Figuring its a fuel issue seeing how i dont lose any boost. Please help!! thanks!

 

Is the maf in the right way,arrow pointing in the direction of air flow?
As you said,all you did was put the stock air box back.

Check the air duct for the air box for a hole between the throttle body and the air box.

 

Yes, it's the right way. I've been messing with this car for the past couple weeks now.