Remove and cleaned throttle body, EGR return tube and EGR sensor. All were pretty carbonized. Reassembled. Don't know if the cleaning was related but my idle in Neutral is about 1000 rpm's - should be 700. When first starting, no problem but engines idle will start to drop, engine will stumble a bit then resume normally. No driving problems or stalling. EGR Valve tests bad, can't hold or attempt to get a vacuum. Where should I start. Will replace EGR valve but I'm not sure if it will change the idle rate. Any help would be appreciated.