Fettuccine carbonara!
Above: EGR plate before. None of the passages were
completely blocked, but one was over 50% blocked (left side of photo).
Clean. Dug out the baked on carbon & crud with plastic and dull metal tools.
Business end of the EGR valve. Sooty, but not nearly as caked as the EGR plate. Filled & soaked it overnight with WD-40 anyway. Also disassembled the "top" (other end) of the valve & inspected the potentiometer's carbon traces (were fine). Flipped the contacts over for a smoother interface anyway.