2002 Chevy Silverado What makes a chevy run lean?

4.8L Check engine light on. Pulled code P0174 System Too Lean (Bank 2). Don't know what any of it means, but here's some data from the scanner:
Fuel Sys 1 CL
Fuel Sys 2 CL
Calc Load (%) 15.69
ECT (deg F) 165
STFT B1 (%) 0.00
LTFT B1 (%) 14.84
STFT B2 (%) 1.56
LTFT B2 (%) 14.84
MAP (inHg) 14.47
Eng RPM 1906
Veh Speed 61
MAF (lb/min) 3.88
TPS (%) 20.00

Not sure where to start. Any help is appreciated.