Yupper, remove those things. The ride is so much better. Your dealer is BS! By leaving those on, you would loose a lot more tire/road contact every time you hit some kind of bump both big and small. You might be thinking, "why are sports car's shocks to stiff then? It feels like I'm sitting on a rock!" When the car's "weight is on the suspension, you want it stiff so you have less body roll and and you can feel the road better so you can control the car better. Take a toy matchbox car with those simple wheels on that rod. Put that car on a flat surface and gently lift the car off the surface. You wont feel the weight of the car not shifting off the wheel slowly but you will feel and see the the car almost simultaneously loose contact off the surface at the same time. It's basically a brick. Now get yourself a good RC car. One that cost lets say $80+. Do that same thig you did to the matchbox. As you lift slowly and releasing the weight off the suspension, you will see that some of the weight is still left on the wheels just to about till you lift the wheel off the surface. Those thing wont let your springs on to extend when your car's weight is lifted off the wheels (when you hit a bump). Less extension = less contact time. Less wheel contact = less control of vehicle. This is why it's so hard to design good shocks. It's tough designing springs that are will provide a smooth ride yet stiff enough to keep the body from rolling left and right during a turn, and yet be able to have the compliance to keep surface contact. I'm just restating the above in simple terms with example to clarify.
on a side note, my new to me nismo with 16,xxx mile had these on them. DOH!!! I have only driven ~30 miles and thought it was extremely weird that my car was rougher than my bros Mustang Shelby. The other thing that was bother me what that every time my car put it's weight back on the wheel after a moderate size bump, the care would somewhat steer itself into whatever direction. I would then have to readjust my trajectory to get to where I was going.
Lets just say the 1st owner is a DOUCH BAG that don't know jack about sports cars.
One for each side.
YzGyz