OMG.....Search Function Wins

I have the SAME exact problem.
Intake, Exhaust, Plenum Spacer, tuned = No CEL Good Gas Mileage
Added ART Pipes, tuned = P1273 and HORRIBLE Gas Mileage

I have 125K miles.

Any idea on how to work around this???
This is quite frustrating.

 

Try unplugging your rear o2 sensors and see if anything changes.

 

Turns out when the tuner puts a effing shitty *** tune in your car. they will run lean....