So I have been using the K&N drop in filter for quite sometime. Why do I get a code with the K&N filter and not with the OEM?
p0171 and 0173

 

Try cleaning your Mass air and T/b.

 

I have dealt with this for some time. There were other codes I received around 120,000 miles which led me to do the following:

Replace fuel filter
4 new cats
4 new O2 sensors
New MAF
New DPFE
New EGR Valve
New EGR Regulator
Cleaned TB and replaced Elbow
New Plugs and Coil Boots
The K&N is clean and pretty with out excess oil. The only thing I can figure is that it doesn't fit as well as the OEM. However the difference driving with the OEM and K&N is night and day with the Hypertech tuning. With stock tuning I cant tell a difference.
GO figure.........