For about a week and a half now my WRX has had a rough idle or I would get hesitation on the highway. It doesn't happen all the time though, somedays its good somedays it's really bad where it's ready to stall at a red light. I called the dealership on Monday, they said bring it in this coming Monday. They asked if the check engine light was on, i told them no. Well yesterday the Check engine, traction control and blinking cruise control light came on. I checked to see what code its throwing and its P0451. Anyone have any input on this? I have almost 19000 miles on it.