If my memory serves me correctly it means insufficent egr flow. I would guess that you probable knocked of the hose the goes to the egr preasure sensor on the back side of the intake. Check the little hose and make sure that it is not brittle or not attached. It should be fine - provided that there are no major other problems, like a broken egr pipe. I would also run premium fuel, because egr is desing to keep combustion temps down, this will prevent spark knock, for the week while you fix it. Also no drag racing either.
Good luck
Tim