Desperate for advice

I have a 1995 ford contour GL, 4 cylinder with 169,000 km. I've had it for 4 months, and just had the mass air flow sensor replaced. And ever since I got it, every time you stop at a red light, or are in park, i've noticed the steering wheel will vibrate, but if I put it into neutral the vibrating will stop. And for the past couple days if I drive it for about 30 mins. Then put it into park, it almost feels like someone is bouncing on the engine, and at the same time, is sounds like someone is reving the engine, going from quiet to loud, also shaking the steering wheel.
so for the confusing description, but I am just so confused.[/Quote]