If you do make any changes, i.e., install a Cold Air Intake, change the muffler, install a new 02 sensor, etc. you should disconnect the battery, get in and turn the ignition key on as if to start it and hold it for 30 seconds, turn key off, re-connect the battery, start it and LET IT IDLE for about 3 minutes DO NOT TOUCH the accelerator, just let it run its diagnostic check of all the sensors and reset its parameters. Doing this should also clear the Codes.
You could already have fixed the problem, but the Code wasn't cleared yet.
Turning the key on is a faster way of re-setting the ECM instead of just letting it sit for 20 minutes.