Speaking from personal experience on my 2001 GTS (12,600 miles so far): The engine will feel a lot freer at 2000 miles than at 1000, and freer at 4,000 than at 2,000, etc. Having put 42,000 on a 97 GTS, I strongly believe that the Viper engine doesn't reach its full potential until 15,000 or 20,000 miles.