I have a 99 3.4 liter 130,000 miles cel p0171 keeps coming up . Has a high
idle on start up after warm idles is good no stalling or surging. 02 sensor are
good . no vaccum leaks found , has a strange noise from exhaust coming
from pas side firewall/floor area sounds like exhaust is hallowed out.
have seen other comment about maf , would failed maf causing bad a/f mixture cause irregular sound in exhaust or double wall construction of
exhaust manifold/headers coming apart cause noise . looking for other solution before dropping exhaust system??
Pull your mass air sensor and look at the wires and see if they look fuzzy with some debris on the wire. Clean the sensor with some electrical contact cleaner and re-install it and see if the code stays away.