[CREWZIN]

Steve,

P1684 is nothing to worry about, forget it.

P0171 is pretty definitely one of the 02 sensors. Here's what I found in search....

P0171 - 1/1 Fuel System Lean - A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

There are a number of possible causes including:

Restricted Fuel Supply Line
Fuel Pump Inlet Strainer Plugged
Fuel Pump Module
O2 Sensor
O2 Signal Circuit
O2 Return Circuit
O2 Sensor Heater Operation
Throttle Position Sensor Sweep
MAP Sensor Operation
ECT Sensor Operation
Engine Mechanical Problem
Fuel Contamination/Exhaust Leak

The majority of tests performed to rule out each component require the use of a DRB III scan tool and or special equipment which most owners do not have, therefore your ability to DIY will be limited.