some one told me that the egr is part of a sensor and its bad cause you might get it to make the piston hit the spark plug cylinder 1 or 4 something to do with measuring the vibration. And something to do with not enough back pressure for the piston. I dont know cause i took mine out from my Ka and someone tried explaining it to me that its bad. I think the kid goes to Ptec in St pete or something like that.