I have a 2004 GT that recently set a CEL code, scanned it but can't remember at the moment what the number was, but it was for an Air Diverter Valve issue. The engine idles as normal but occaisionaly and more often than not, under a load the engine vibrates fairly heavily. It isn't the plugs, tried that already, and the vibration under load only appeared as soon as the CEL came on initially. Any of you ever had any dealings with this thing and if so, where is it located on the engine?