It's not a crown vic, the transmission keeps the engine engaged when you let off the throttle causing compression braking, in generally cheaper cars when you let off the throttle it just keeps going because the transmission is slipping (it's a sports-like car, this is completely normal)

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2006 BMW X5 4.8is Lemans Blue/Beige/Dark Maple
-Nav, Comfort Seats, Heated Steering Wheel,
Rear Airbags, AUX Input
2009 BMW M3 Space Grey/Black/Carbon
-all options