Headers, cut the flanges or not??

If you're talking about the header to head flange, you can cut that between the three sections. Some older brands of headers used that design and there's nothing wrong with it. I've even heated and bent the center flange between the ports to get more pressure accross the center. Whatever you have to do, just don't overtighten them, and re-torque after they've been run (heated) and allowed to cool a few times.