220rwkw is pretty good, is it an rb20 hiflow or an rb25 hiflow? I thought rb25 hiflow are good for ~260rwkw..
It's not so much about the size of the engine as the size of the turbo, if the turbo can flow enough air to make 260rwkw, it will make 260rwkw (within reason), if it's on a 2L it will just take more revs to make the power than if it was on a bigger engine.
You can get more than 300rwhp out of an RB20 but the size of the turbos required means it would be quite laggy and come on boost REAL hard (i.e. lag lag lag lag WHEELSPIN).