Opinions vary, but they were installed to damping the vibrations on convertibles only. (lack of roof for stiffness) GM's way of solving a problem. Some like'm some don't. Regardless, in good condition they are worth good money. BTW they are called "cocktail shakers". They add about 100 pounds extra to the car. Unless your building a 1/4 miler, you wont notice too much of a difference. I say leave'm in!