I have a "91" Eldorado 4.9 with 138,000 miles that is idling rough, and also has a consistent miss. The engine rpm's are also rather high at start-up before quickly setttling down. I have put on a new EGR valve, Cleaned the throttle body, Put on a new distributor & Wires, New air filter. In spite of this, the rough idle and miss continue. The plugs were recently changed about 9 months ago, so I don't suspect a problem there. Could my problem perhaps be vacuum related? Any help would be greatly appreciated!