you fudged up never use additives in the coolant get rwady to replace the radiator and heater core
good dont is it thr rad for sure that is leaking
my car also has a leak some where but i cant find it i just add a quart every month or so
have you repaced lim gaskets?
a person with basic knowledge can do it. the kit is like 90 bucks at advance but i comes with everything you need except the supercharger gasket
there is a video on how to do it first go out to your car and look in between the head and lim if you see black plastic gaskets replace them if theres metal its been done before
wish i had a picture to show you