How to tune an edlebrock Q-jet carb?

I have an eddlebrock quadrajet carburetor on my 1987 chevy el cameno it has a 5.0L 305 that's running really really rich and i need to learn how to lean it out. as it is right now it idles good and once it gets ped about 3000 rpms it runs good but from about 1200 rpms to about 1700 rpms it spits and sputters and skips i just put a full tun up in it so i no it has to be the carb