Last thursday, I was driving home from school when my MIL came on. it was running fine and all the fluids were good. so i took it to auto zone and had the codes checked on it. it came up with EGR Flow Insuffiecent" so the guy gave me fuel additive and told me to use premium and it should go away. well, i've done that and the problem still persists. any idea on what to do from here, or what that actually means?