I've got a 650 Thunder series carb. The instructions say the front nipple is for the PCV valve. There is a port out the back side for power brakes. If no power brake port is needed, you are supposed to cap off the port with a supplied plug. The instructions say NOT to hook the PCV valve to the rear port. My question is why?

Isn't manifold vacuum the same no matter what port you use? I want to run an oil vapor separator mounted on the PS inner fender right next to the firewall. It would be a much cleaner install to run the line to the rear of the carb. I do not have power brakes.