I have a '02 Ranger FX4, 4.0L, 5spd with about 160k miles on it, and have recently been getting a CEL for P0171 (Bank 1 Lean). The strange thing is that it is NOT throwing a code for Bank 2 being lean. So far I have replaced:
MAF Sensor
Fuel Filter
Upstream 02 sensor on Bank 1 (Bosch)
I also...