When i bought the car this was tucked into the fender

 

It's your electrical/vaccuum solenoid which was attached to the factory airbox. It was used to open up another intake flapper in the stock airbox for more air. I have attached a pic on it.
You must have an aftermarket installed. With aftermarket intakes this is not necessary, however you must still have it hanging around and it must be plugged in electrically! You should see there is an electrical plug in for it which is also green. Leave it plugged in and tie it up. Show us a pic of your intake.
I also included a pic with an aftermarket intake and you can see the green solenoid hanging around but still plugged in.

 

I'm putting in a new CAI tmw injen...the problem I'm having that's its throwing a check engine light, is there anyway around that?

 

1) Disconnect negative terminal on battery and step on brake pedal for 10 seconds. Wait 15 minutes. Re-connect Negative terminal on battery. Now re-learning starts. Let it idle for at least 10 minutes before driving. Hopefully cel doesn't come back on.
2) If it does come back on then you need an air straightener----it is something that helps to decrease the inside diameter of the intake (as this is what is throwing your cel). It's purpose is to straighten the air before it hits the MAF sensor so that it will produce more more consistent measurements.
Don't know if these exist anymore: AEM Mass Air Flow Straightener

3) buy one of these power module unit: http://www.twisted-visionz.com/Online-Store.html