Yeah, that left side looked sketchy to me. You can see a little hose below the T connector that connects to the firewall. That could probably be the stock firewall port you were looking for? My gut tells me that metal pipe is rusted so he bypassed it and routed the new rubber hose to the rear blower. It's actually working right now, but I'm going to do the rear heater delete.
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Does removing the rear heater do anything...? I mean, other than adding heat to the rear of the rig (I assume)? What does it DO for you?
Thanks,