1994 Chevy Caprice A/C leaking into passenger side floor

No, it is not condensation or rainwater. To clarify further, water is running out of the drain tube in the engine compartment like normal but unfortunately it is also leaking into the vehicle. After the carpet was drenched I realized it would need replacing so I cut the carpet on the passenger side. I also put a slit in the rubber by the firewall so that I could see where it was leaking. I can see that water is leaking from under the "seal" that is between the part of the a/c unit that is bolted to the firewall inside the vehicle. That is when I tighted the bolts protruding in the engine compartment and the leaking stopped for a week but has since begun to leak again. It only leaks when the a/c is on. Can the seal be replaced or can I use a sealant or something else? Or what else can I do to stop the leaking into the car?