Months after replacing my heater core, I lifted up my floor mats to find the dreaded wet carpet from an undetected leak. While "fixing" the leak (thinking it was coming from the o-rings) I busted the plastic connector system that runs through the firewall. I could only find this part through the dealer, but to my surprise it only cost $42 out-the-door, including All the o-rings and clips! IPD and FCPGroton charges that for JUST the o-rings and clips. Just thought I'd pass that along. Also, I found that if you loosen the two torx screws holding the metal plate on the engine side of the firewall, you'll allow the connector to move a bit when you're replacing the heater core so you won't break the old, fragile, plastic connector like I did. Replacing the connector was fairly easy.

Cheers,
Brent