Chevrolet Repair: 1992 Chevy Caprice Idle Problem, intake manifold gasket, vacuum leaks

Question
I have a 1992 Caprice Classic w/305 TBI.  It has 94,000 miles on it.  After the car is warmed up and you stop at a long traffic light; with your foot on the brake the car idles roughly (only when you press the brake pedal).  I have replaced new the cap, rotor, plugs, wires, fuel filter, air filter, EGR valve, alternator, battery, entire cooling system, checked for vacuum leaks, checked brake booster for leaks.  I dont know what else it could be but the TPS sensor or idle air control motor. Can you give me advice on what to do or suggest.

Answer
Hi Chris, Would like to feel the rough running but I can't. I guess I would disconnect the vacuum from the brake boaster and see if that stops the problem. Then if that didn't do anything I would remove the pcv valve and plug the hole. Now run the engine and put a vacuum gauge in the other hole in the other valve cover, you should not have any vacuum. If you do the intake manifold gasket is bad.

Hope this helps

Have a Great Day             Mark