I think it attaches to the stock airbox. I'm not 100% sure tho because when I got my car it was just dangling by the boost hose because it had no airbox.
Have a look near the bypass valve, there should be a boost hose coming off the side of the intake pipe that should go to a t-piece that splits the hose, one hose goes to the wastegate actuator and the other goes to the boost solonoid. All you have to do realy is remove that t-piece and put your boost controller between the hose that comes off the intake pipe and the hose that goes to the wastegate actuator. Then find where the boost solonoid is, it should connect another hose to the pipe between the maf and the turbo, you should plug up this hose some how so you dont get air being sucked into the intake from here, just put a screw/bolt in the hose and cable tie it n or something.
I hope this helps and makes sence.