all fluids have a tendency to create a whirlpool effect when draining from one area to another. however, our intakes aren't really drains, more like pipes directing air from point a to point b. I highly doubt that it will make a whirlpool. I also agree with Maxvla that it is travelling further when swirling and we clearly want to ram as much air as fast as possible, so making it travel more seems to go against any increases. Now it would seem advantageous to swirl the air if you are using it to increase pressure in say a.....Turbo system!!
That's a whole other story though and it isnt a whirlpool either, so I'll just drop that.
Scott