Having problems with a 2001 Deville it has the 4.6 Northstar engine. Had the plenum boot replaced a couple of days ago, new spark plugs and cleaned the throttle body which was really bad. The car still ran rough at idle and under load so the mechanic suggested it may be the front coil pack so I replaced it yesterday. Still getting the 0300 code random misfire. The car runs great cold now but as soon as it warms up it starts to act up. Runs rough,surges at idle, bogs right out under load and the engine light starts flashing 0300 code only. One thing I noticed today was that no vacuam is felt at any of the small vacuam lines going to the various components. Was wondering if these were plugged where they connect at the throttle body and how is the best way to clean them.