What is this supposed to be plugged into? Kind of just found it stuffed to the side in my engine bay, is this for something important or maybe an accessory?

 

It goes to the VFAD solenoid which was located on the back of the factory airbox. It's not used with an aftermarket intake.

 

Thank you

I'm still figuring what the previous owner did to the car.... it's longer process than I thought

 

Give you a hint. Get rid of that eBay cold air intake. I suspect you have rough idle and perhaps even a miss at idle and can feel surging on the highway. That is due to that CAI it has nothing to straighten the air before it hits the MAF. Giving your MAF bad readings and in turn giving the ECU bad info. It also will rob you of so HP. Get a AEM one or find a factory set up.
Post some more pics and we can help.