rough idle speed

I Just Bought A 1994 Buick Lasabre 100.ooo Miles Has New Plugs
New Plug Wires New Fuel Filter But. The Engines Idle Speed Is Rough Like It Is Missing Get It On The Highway Runs Like A Dream
Doesnt Matter Cold Engine Or Hot Engine Still Rough Idle .
Somebody Told Me To Replace Mass Air Sensor Did So Still
Rough Idle You Can Unplug Sensor Seems To Improve Idle Speed.
Whats Up With This Any Help Would Greatly Be Appreciated.

found the problem replaced o2 sensor it had never been replaced before it in return had made the egr valve unresponsive now it idles like a dream oh! by the way thanks for the o responses to my problem.