EGR Issues Again

[732Galant]

This is an issue that appears to arise when I have to go to inspection. Two years ago car threw a code for EGR Flow Malfunction. Replaced egr valve, still was on. Come to find out the intake manifold gets clogged with carbon and thus triggers the computer into thinking there is a flow issue. This year it comes back, I clean out the carbon (again), clean the egr valve, vaccum test it, check to see if it opens and closes as it should manually grounding it. All lines are clear, everything checks out voltage wise, vacuum wise, etc. All is well. The CEL wont go off though. I have had it turned off with a scanner twice. It comes back on in about 15 miles or 25 mins or so of driving. Any ideas would be appreciated.