Harrydactyl

Hi. I recently put on a cold air intake on my 2011 Scion TC. After pulling off the highway after about 40 minutes of driving the car started surging and the idell started around 1800. When I first installed it, I let the car idel for about 5-10 minutes. It was perfect. I was able to drive it around the city with no problem. I doubled checked the clamps. Everything seemed tight. This all happened within the same day. I was thinking possible vacuum leak. Does anyone have any idea what this could be?