I never messed with the kits from autozone before so i dont know what is available, however i do know that unlike r-12 where the more freon you have the colder the a/c is, r 134a is`nt that way. You should have a decal under the hood which will tell you how many lbs/ oz. to put in. with r-134a too much or too little will make it not work properly.where i work we use a vacuum pump to remove all the air from the system and a digital scale to put the exact amount back in. someone who works with a/c frequently can also do this just buy looking at the gauges but i imagine since they sell these kits now at autozone for some time now it should all be in the instructions