jumpy idle

i have a 93 3.8. the cams have been re-ground. would that cause the car to idle rough?? the motors been completely rebuilt about 2 years ago (30,000 miles). when the car is idling, the needle will jump a little and the car will shake. it does it about every 3 seconds. i thought it was a vacuum leak at hte pcv valve, because i could hear it. so i changed it, and the roughness seemed to diminish. but then it started again. its not really noticable, but i can feel it. any suggestions??

I don't know if you have done this, but for what its worth, I would give that bird a complete tune up. Wires, plugs, air and fuel filter. Something simliar happened to a Firebird I once had. The culprit there was a mis-fire in one of my cylinders due to oil in the cylinder. But if you havent tuned up your bird recently, thats probably the culprit. Could also be a sensor problem.