[import.only]

I just dropped a new engine in my 96 3500. It was a remanufactured 350 vortec. I got a check engine light right off the bat due to incorrect timing. Fixed that, but now I get a check engine light that is on some times and off at others. The fault code is "System too lean (bank 2)". Can some one point me in the right direction with this problem. Thanks.