I solved the coughing when cold problem, by changing the airbypass valve. But it still surges thru all power settings. I found the EGR valve clogged, so I replaced it along with the EGR vacuum solenoid, as precautionary. And still no help! Could I have some clogged injectors? But, if so, why is my problem intermittent? Does anyone have any answers? Thanks, Elwood