Can I do this?

Is it a good Idea to drive like this?

I do normal driving in D4. At about 2000 rpm, I shift to D3, I feel a sudden boost in power, then at about 3000 rpm, I shift down to "2" and then, you can REALLY feel the car gettin boosted. Was lookin at my rpms and it went from 3000 rpms to 6000 rpms in a matter of a like 2-3 seconds,and If I didnt let my foot off the pedal, I think it woulda went into the red zone (maybe I dunno).

I only do this a couple of time.. Should I be doing this? Does it my hurt my engine or damage anything??