If you are throwing a lean code, you want to get that fixed ASAP. If you drive "spirited" you might be ok, but the more your engine demands fuel, the closer you get to the danger zone. If you added the CAI after your tune, then Mustang Phil is exactly right, a tune will fix you up.
Driving too lean can literally melt the pistons out of your engine. Don't ask how I know that. Of course, that's a worst case scenario, chances are you aren't doing any damage.

 

Hey Lupin. Oil affecting the MAF sensor is a subject that you'll have to agree to disagree. I've experianced the malfunction myself. I oiled the filter knowing it might affect the MAF but did it anyways. The next day I cleaned the MAF and bought a new filter on my 03 GT due to rough idle and lean codes poping up. K&N is a good company selling filters and CAI's. They claim their CAI will give you 7 to 10% hp gains on my model car, but thats just not true at all. The most you get is a 1 to 2% gain. I don't think they would advertise their deffects and still expect gains. I do agree on O2 sensors throwing lean codes but usually it's a p1151 or p1152 code that's a almost sure thing an O2 sensor is bad on one side if not an exhaust leak. The car usually pings in high gear with lower RPM. Thanks CPTCO. Americanmotorsport.com helped me with my tuning and helped me trouble shoot some issues with lean codes and a bad O2 sensor. I would recommend them to anyone. Great customer service where others have failed for me.

 

Once I got the MAF cleaner and did the sea foam it's running perfectly with no codes whatsoever. Thank you all so much