Ford Repair: erratic rpms, throttle position sensor, motorcraft spark plugs

Question
I HAVE A 1993 FORD TAURUS SHO 3.2L. WHEN I START IT THE RPMS ARE ABOUT 1000. I DRIVE IT ABOUT AN HOUR AND WHEN I COME TO STOP LIGHT  THE RPMS DROP TO ABOUT 500 AND IT FLUCTUATES IN BETWEEN 1000 AND 500. I TOOK IT TO 3 SHOPS. TO HAVE IT DIAGNOISED.ONE MECHANIC SAID EGR VALVE AND SENSOR. I CHANGED IT NO CHANGE. I ALSO  CHANGED, FUEL FILTER FUEL PUMP  MAP SENSOR, TUNE UP, O2 SENSOR,THROTTLE  BODY AND SENSOR,AND CATALYTIC CONVERTER, ANOTHER MECHANIC PUT IT ON MACHINE AND SAID IT IS  NOT THE ENGINE,IT WAS THE CATALYTIC CONVERTER SO HE ADVISE ME TO CUT THEM OFF. STILL NO CHANGE. PLEASE HELP ME I DO NOT KNOW WHAT ELSE TO DO. ANY HELP WILL BE WELCOMED.  

Answer
Sometimes carbon will build up in the throttle body causing this, but since you replaced it, that is ruled out. Do you have the OEM spark plugs in? I know that SHO's are really picky about the spark plugs, but usually it will just fall on it's face. Use Motorcraft spark plugs. Don't cut the catalytic converters off. Use a different mechanic. Did any of these rocket scientists put you're baby on a Genesis scanner before they started throwing parts at it? Usually this is caused by either a throttle position sensor or idle air control valve. The ECM itself may be on the fritz. Have it put on a scanner, then you will know for sure what the real problem is.