I installed an Injen cold air intake along with a magnaflow catback system. I noticed a lil while back that my car was "lagging" or "stalling" a little outta first and second gear. It got worse and eventually the check engine light came on. I'm almost certain it's my O2 sensor not reading right because of the intake, but I dunno??? Any suggestions or advice??? Thanks!

 

You may not like my suggestion, but I think you'll be much better off by putting the factory intake back on and throwing the Injen in the trash.

 

Your O2 sensor should not be impacted by your intake. You need to get a read on what the CEL is.

 

+1 get the CEL read and see what it is. My money is on an issue with your MAF, especially since you said you had problems when starting in 1st and shifting to 2nd. A common issue that's arisen with those who've installed intakes is that unless you either extend the wires on the MAF harness or unclip the harness from where it attaches to the battery box the wires just barely reach to where they're supposed to be (or with very little slack). When the engine torques, and especially when starting out or doing the 1-2 shift, it pulls on the wiring harness. That can cause stretched/broken wires in the harness or issues with the pins at the plug.

If the code comes up as something pointing towards the MAF then I'd recommend checking the harness and plug to make sure everything's working well. If you don't have the tools/know how to do it then any competent mechanic should be able to check the continuity of everything in the harness to make sure it's working properly.