I own 2004 480 sedan with twin qsm 11's. Occasionly without warning the port engine will lose power. Cruising at 1900 rpm etc. and Rpm will drop to approx 1100 rpm. Engine power will resume to normal after few minutes and process will repeat itself. Raacor filters have been checked and indicate no issues. Fuel is fresh and clean. Engine will also occasionly sputter when at idle.