Apologies in advance for a likely very basic question - I am new and trying to learn. I have a Ford 302 that I installed the Edelbrock Pro-Flo 4 kit on. The engine starts easily and runs fine, but at idle it has a loud hiss. I checked all of the vacuum ports and these are either in use or capped off. I have isolated the noise to the throttle body and noticed that at idle the blades are almost completely closed. There is a screw to adjust on the side, which can open the blades slightly. This reduces the hiss, but also increases the idle fairly substantially. What am I doing wrong?