I checked my check engine light and i came up as the rgf? (i forget) insufficient flow. It is the thing that sits on top of intake manifold. The people at advance autoparts said to just replace that item. I later took it to my mechanic who has done all of my work and siad my intake is clogged with carbon. My car seems to be running very rich my exhaust being black and my entire back of my car is black. Any help in which route i should go or anything would be greatly appreciated.