When I stop it leaks what appears to be water out of what looks like a curved overflow tube coming out of the firewall on the passenger side. Any idea(Kia Optima 2004)

Are you running your ac cause that sounds like the condensation drain tube

I have a strong hunch that what you're refering to is Condensation that is on the outside of the air conditioning tubes. These tubes can get really cold and the moisture in the air can condense the water into ice on the pipes, then when you stop, it warms up and the ice melts and appears to be water dripping from your car.
After running your a/c for a while with the car running, stop and open the hood and check the aluminum tubing near the firewall. If it's icey and melting off, this is quite normal and nothing to be worried about..