Was pulling a pretty steep pass today with my 06 and a 4500# camper on its back and i would intermittently loose all boost. I checked my codes and got a P0299 (loss of turbo pressure) and P0478 (exhaust pressure control valve malfunction) obviously first code was caused by the P0478. Is this an easy fix or a shop job. Where is the Exh Pres Control Valve located? Any suggestions are appreciated.