shaking problem

I have a quad four 93 grand am gt. At about 70mph if I'm deaccelerating (ie letting off the gas pedal) I notice a slight vibration in the car. If I press the clutch the vibration goes away. I've recently had new rotors/pads and outter tie rods put on the front. Its also been alligned. Its a lot better than before all that work was done, however its still not quite right.