whats causing check engine light/vtc code?

Question

I have a 2008 Civic SI i recently had the valve cover removed.. while doing that i also changed the spark plugs.. drove the car roughly 100 miles and a check engine light came on.. i had it checked at advanced auto and it came up the vtc was stuck in advanced position.. the car is idling high and not wanting to accelerate any clue whats causing this?