Your car is equipped with a clutch delay valve. If you drive your car hard I suggest you take the valve out (really I think everyone should take the valve out).
The clutch delay valve makes the clutch engage at the same rate no matter how fast you shift.
In other words, your clutch is doing a bunch of slipping every time you throw a shift. Google "Challenger clutch delay valve". There are a bunch of videos on how to remove it. It's a very simple, zero dollar, DIY project that shouldn't take more than 30 minutes.
