Hello,
I hate lean codes. Honestly, it could be anything related to air metering (MAF, Oxygen sensors, IAT, etc.), fuel regulation (injectors, pressure regulator, fuel pump, filter, etc.), ignition (sparkplugs, wires, coil pack, etc.), or compression (head, head gasket, rings, etc.). These codes are tough to remedy. It could be as simple as cleaning your MAF, or it could be as painful as replacing a cylinder head or piston rings (requiring a rebuild).
Check out some of my previous posts regarding my personal struggles with these codes. My first lean code run-in turned out to be a spark plug. I had a second one which turned out to be faulty upper intake gaskets. I also had a third one, along with some coolant seepage, that turned out to be faulty lower intake gaskets. I've heard of others with the same codes caused by any one of the above items.
Please describe your driveability problems as accurately and articulately as possible. When you drive, does the engine hesitate or "skip", like a misfire? Do you lose power under wide-open-throttle? How's your gas mileage? Do you have any coolant leaks? Any and all of these subtle clues will help us narrow this down.
Good luck,
ERUSH