engine problem
 

also posted in chevy forum
i have a 99 5.3L sierra with around 115K on it and I have some problems! around labor day i had a problem with cold starts, it would start fine but idle rough then smoothed out once warm. sounded like fuel problem so changed fuel filter, then plugs, then fuel pressure regulator, nothing worked. check engine light finally came on, said banks running lean leading to O2 sensors, changed them also with no luck. finally this weekend it turned for the worse to where i decided not to drive it. check engine light still read banks running lean. wondering if anyone has any ideas or has encountered this problem? i thought maybe injectors??? thanks in advance