bought the Tanabe's today. When you guys lowered your car did you keep the rubber insulator between the bottom of the strut and the spring? Most cars don't have that piece.

 

That's the bushes, you can if you want.

They are there to help minimise the vibration and movement going from the springs into the body of the car. If your putting harder suspension in, you may not even want to have the bushes in there, but it depends what you want. And if it is harder suspension, I assume your putting a strut bar across the engine bay to help minimise chassey deformation.