I am throwing "Secondary Air Injection System Malfunction" and "EGR flow insufficient" codes. I am guessing my EGR valve is bad, my roomate says it might be the check valves on the AIR pump. Regardless, I'm kinda trying to hold off on changing either since I plan on getting non-emissions headers in the next 2 months. However, since the light came on, my gas mileage has dropped from like 200 a tank (city) to about 170 a tank. Do you think either one of those things could have that much impact on my fuel mileage?

 

I would say no, because I just put headders on and deleted my EGR and rear O2's and have noticed no change in gas mileage. But TTT for you cause I'm curious too.