The only real performance difference in the police interceptor and regular crown vic is the extra cooling engine and trans, suspension package, the computer. The compute has different air, fuel, timing curves, and a higher speed limiter. This allows for quicker off the line and high speed pursuit. There is no difference in the engine or trans itself.
For Ford to save the crown vic it would have needed total ground up revamp to keep up with competitors. It has gotten old, out dated, and slow.
Here is fords new Interceptor line. IMO It's better in most ways than Ford competitors.
2012 Ford Interceptor Police cars revealed - YouTube