what package do you have for kts? it gives you a full test procedure for the egr. if pin 4 had importance ie was for sensor feed back it would give you a procedure to test that looking at, also there is no symbol on the egr that states it has one. you only have the transistor, mechanical component and coil symbols . I would try looking for a air leak, blockage or as was said the air mass.If you would like i will message the full test procedure over.