High revving of engine 5000 - 6000 rpms until it warms up on a 2000 VW New Beetle?

If your doing it on purpose then DON'T.

If the engine is doing it via the computer you need to take it into the shop and have them look at it. There seems to be a bad sensor telling the computer wrong information. Running at a high rpm when the motor is cold and with no load is not good for it.