4k is way to high, unless you really ride the clutch, that will do nothing but spin the tires.
The optimal launch rpm depends mostly on your car. The weight, tires, type of pavement, etc. Can all make a pretty huge difference on your launch.
For a stock SVT, the best launch is 2500-3200 depending on conditions. It should be just enough to lightly spin the tires for about 1/4-1/2 a second before catching. This will prevent your engine from bogging, and will prevent you from riding your clutch hard. For me, that has given me the best times without being absolutely abusive to the drivetrain.