Another idea: You mentioned new EGR - did you mean the valve?
- Was the pipe gunked up as well?
- I only know this academically b/c I don't have this on my car anymore but I seem to recall that a closed EGR could cause knocking. A real professional mechanic like madmikey could confirm this theory.
Whole thing (not the pipe though, it appeared fine). The valve and the solenoid. That was the post I did a while back about the wiring to the plug...did I have the right wires to the right spot.. I think I do.