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The F45 is Real Time Dampening and the F55 is a Selective Ride Control. It uses a magnetic fluid in the shocks that give a faster response.
As far as lowering an F45 , which I have, is from what I have read, is if you lower it to much, it will cause the shocks to think that you are constantly on a rough road surface making them work and they will go out sooner. Again only what I have heard. I know there are pros & cons on lower an F45 car, some will say no problem while others say don't do it. I do know that to get at the front bolts the shocks need to be removed or at least on the lower mount.