Stiff brakes and Sputtering engine

I have a 2004 Bmw M3 the car is absolutely beautiful with very few defects.

Recently I have been experiencing some problems.

After a couple of days of not running the car the brake becomes very stiff, this part of the problem does not concern me as much as the next part...upon the starting of the vehicle the rpms will spike to over 2k and then suddenly drop almost to the point of the killing the cars engine..

My question is what could be causing this? Should I be concerned? is any one else having this problem. Thanks in advance

John.

The second could be a fuel pressure problem. Try turning the key to ON, but don't start the engine for 30 seconds or so.