I had the "engine" light come on about 6 months ago. I had Autozone check the code. It came up "EGR valve insufficiant flow" or something close to that. I bought an EGR vavle factory direct off of ebay and put it in. I cleared the code (disconnect battery). But after driving a few miles the light came back on. I had Autozone check it again and it came back the same. What am I missing? It is just a plug and 2 bolts.