93 Grand Am Intermittent Bucking/Stalling

Hello! I have a '93 Grand Am with 200,000 km on it. It will intermittently start bucking accompanied by a noise that sounds like it may be grinding or intense vibration coming from the engine when I begin to press the brake. This usually occurs after I've been driving the car for more than 20 minutes and is more likely to occur if I'm going 70 km/hr or more then coming to a stop. I am sometimes able to throw it into neutral upon hearing the noise to prevent it from stalling, and once I throw it back in drive and give it gas, it will run normally again. The car idles poorly normally, but not to the point that you think it's going to die.

I had brought it to a mechanic several months ago when the problem was prominent and occuring very frequently. He took it for a drive and of course the car wouldn't act up for him, so I really didn't get any information other than that it could be the MAF Sensor. At that point, I cleaned the sensor and the car seemed to work fine for a couple months, though I only used it driving 10 minutes to work and back.

I took the car on the highway and now the problem is occurring more and more frequently. I have since replaced the MAF Sensor and Fuel Filter, and the problem is still occurring.

Any information/suggestions would be greatly appreciated!! Thanks!