Originally Posted by seminaryranger
A Vacuum leak.
I know the OHV 4L (like mine) would develop a vacuum leak due to a failed upper intake manifold gaskets. I also had to replace the gasket beneath the fuel rail.
But you have a SOHC judging by your avatar.
I would still suspect you have a vacuum leak if your getting a lean code for both banks at the same time.
OHV 4Liters are know for getting vacuum leaks and it could be b/c the upper intake manifold gasket is bad??? Dang that sucks, i have a vacuum leak, could be what it is. Still havent had the smoke check done yet