Has my 93 4.0L got weird vacuum line plumbing? Can't find where it goes thru firewall
I'm trying to trace a vacuum leak that's causing problems with my climate control. I've found the correct vacuum line as per the routing diagram inside the engine bay (it says it supplies climate control, cruise control and 4x4 axle), but the weird thing is that it doesn't branch off through the firewall. The line just comes up off the manifold, where there's a check valve, and then it goes over to the other side of the engine bay and into the cruise control and the vacuum reservoir under the battery.
It doesn't branch off through the firewall at any point, and I can't see any obvious empty holes in the firewall for it go through anyway. The only clue is that where the line is running about level with where the climate control unit inside the cabin is, there's a capped-off junction.
Any ideas? Does the 1993 use some weird vacuum hose routing where it's not obvious how the line gets through the firewall?