Clean the passages. There's great instructions here if you search for them. You'll need an egr gasket and a tb gasket, iirc.
If that doesn't work, it could be the DPFE. That usually throws a different code, iirc. Search on DPFE and you should get some discussion about it.
Those are what I would chase.
I would also inspect every vaccum line I could find. Vaccum leaks can wreck havoc on the intake system.
Scott
