Should I mill my edelbrock performer rpm intake?

I can tell you this. "However" you get the bolt holes to align perfectly, is how you should run it. If the bolt holes are aligned, then the ports are aligned about as good as you can hope for. On mine, I ended up using JUST the intake valley pan gasket right by itself and it lined up perfectly, so that's all it got. With a liberal coat of K&W Copper Coat of course.