Hey guys, I have a 95 that overheated today. The steam was coming from the firewall, could this be the heater core?

It sure sounds like it to me.

agreed, most likely the heater core or related component. but i have seen steam come through my vents when the heater hose inside the engine compartment blew a hole.

something to note; what happened first the over heating or the steam? it may be over heating due to a clogged/faulty thermostat. which along with a bad radiator cap or clogged boil over hose could have caused your system to boil the antifreeze and build pressure till pop goes the heater core,.. it's worth looking into. pull the boilover hose off the radiator and blow in it, bubbles should be heard from the reservoir.next remove cap (cold) and check that it is clean and free too pop off at 15 (ish) psi. while you have your system empty pull the three bolts to your thermo housing and inspect thermo for signs of sticking open or closed. i say this because you have no idea how many times a friends car has overheated and i pull the radiator cap and thermo to be covered in that nasty (but effective) leak fix crap and causing the thermo to not open properly and cap to not relive the pressure till something pops or leaks.

another nifty trick with thermos suspected to be bad is to boil them. if they open all the way up in boiling water them they r working ok.

hope this is helpful.