Re-check your installation work. You likely have an air leak after the MAF.
After installing a SRI, you should disconnect the battery to clear the previously learned adaptive fuel strategy settings and let the car idle for a few minutes after restarting.
DTC Code details:
P0171 - System too Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. For lean and rich DTCs:
Excessive fuel pressure.
Leaking/contaminated fuel injectors.
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Vapor recovery system.
Induction system: Air leaks after the MAF. Vacuum Leaks.
Improperly seated engine oil dipstick.