it will actually decrease flow if done wrong. and if you leave it rough it will help atomize the fuel better for a more powerful charge. look at all the high dollar CNC ported heads, the intake runners are rough for that reason. Hinkernel (sp?) thought me that trick. you can kinda see it in this picture. don't mind all the brokeness, its an LS7 C6 Z06 head.
http://i25.photobucket.com/albums/c80/CamaroAJ/JasonZ06001-1.jpg