I've had the same problem with my car since I bought it 3 years ago. I replaced all the usual tune up items as suggested on this forum, still have the problem. I read the post recently about cleaning the MAF sensor with electronics cleaner.
Today I sprayed the MAF sensor, throttle position sensor and the other sensor that'* in the front of the throttle body (don't know what it is) and the sensor that'* in the rubber intake hose just before the throttle body (don't know what that'* called either).
Went for a test drive, and the car still shudders under load while in overdrive. Still don't know what the problem is. Car is a '95 SE with 155,000 miles, I bought the car with 122,000 miles, like I said, it was shuddering when I bought it.