2003 Infiniti G35 Code P0171 too lean

I have an 03 G35 sedan with check engine light code p0171 system running too lean. Car starts right up, but i feel it dose not start up as quick as it should be. Now the car or engine does feel little shaky when first start up on parked position. when driving no shakes only when put to neutral comes back a little. Also, when i add gas to the car the gas gauge didn't go up or change. No smoke or anything comes out of exhaust. Otherwise car drives strong with no idle or shutting problems.