problem system to lean '02 Trans Am

[gcross]

I just got some new codes P0171 (system lean, left bank on 4 sensor) and P0174 (system too lean, right bank). My question is what does this mean (beside it's running lean) and how do I fix it. The car is hard to crank with out pedal work and just turns off when running. I've never had this problem before the car has always ran rich before. O2 trans am, LS1 with LS1 hot cam 90mm throttle body an several others mods. Any help would be great. Also the long term fuel tables are at 25% avg, but short term is good at 3 to 4 %. LC-1 wide band is reading 12.7 avg at 1.8 volts. HELP.

thanks
Gary