my 94 ciera cutlass(3.1L) started shaking really bad when im on the highway cruising at 55-65 mph, it has also lossed alot of power since it started happening. it started with it happening once in a while, and just got worse after that to the point that it does it everytime u get up to speed and when u stay between 55-65 mph but if ur going faster or slower u cant notice it as much. i need help with this bad!!!