Buy lighter wheels. Stick with Michelin PSS for the tires -- they are on the lighter end of the range. Some BBK save weight over stock due to the aluminum rotor hats and aluminum calipers even though the rotors are larger and steel.
For sprung weight, try a titanium exhaust like the Akra. Also the stock seats are heavy. Try Recaro or Sparco seats.
I think you want that Porsche 991S that you test drove. The car is about 10% lighter and has about the same power as the M3. Plus the ceramic brake option is only $8k if you insist on minimizing unsprung weight. You can have AWD for the snow. Perfect daily driver/year round beater for New England.