What do you mean anti-freze comes out of the cap (if anything it should pass thru to the overflow bucket)? Is it still doing this? Did it use to do this prior to your head gasket change? Do you have water in your oil (is the color of your oil like a chocolate milk)? Have you done a compression check (hot and cold)? If there is a vacuum leak, get a can of ether (starting fluid) and start spraying it around...see of the RPM jump up, then isolate the area (BE CAREFUL NOT TO IGNITE THE SPRAY AND USE SMALL AMOUNTS CAREFULLY). One more thing, because of the "anti freeze coming out the cap", I would put a pressure tester on the cooling system to try and see any problems there (you may have an exahust leak into the cooling system ect). Good luck