hello i have a 2001 gmc sierra, and im having problems with it starting. when started in the mornings it acts like its going to be fine but after 2 seconds into the start up it will idle high for a quick minute and then acts like its trying to die like sluggish, i have replace the plugs and wires, fuel filter, and have only cleaned the mass air flow sensor. please help i would like to know what dirrection i should head next with keeping costs as low as possible. thanks for your time.