Still can't figure out why check engine light is on.

So I've been having this problem for about a year and I still haven't figured it out. I pulled the code and it said it's an egr problem so I swapped out my egr out for a new one. And no dice. Reset my hazard and the code still came up. I don't notice a problem besides the car shaking when stopped sometimes. The engine light turns on after a while I notice it turns on when the car accelerates (automatic). I've changed my valve cover gasket twice. Another problem my ac doesn't work so could that contribute? Anyway I hope i can get this problem solved. Thanks!