there is a tunnel that parallels the main line
I think you are referring to the tunnel that parallels the main line from just above Not My Fault and reconnects back at the Change Up. It first breaks off just after where the pull rope ends; the jump is off to the left around a corner as you're swimming in. This passage is a tight sidemount only passage. It drops down another Fault (It is Your Fault) after 100-200' or so. The passage parallels the main line and has one short jump (to the right as swimming upstream on the main line) at around the 1200' marker on the mainline (between the entrance and exit to the Gnarley Way Circuit on the left side of the main tunnel). This is probably where you picked up the circuit. If you keep going upstream another 100-200' you run into another tee. One line goes straight ahead about 20-30' and dead ends. The other way goes off to the left (as swimming upstream) and reconnects to the main line at the Change Up. When we did the new map in 2003, most of the parallel tunnel is on there except for the fault portion. The arrows were left pointing upstream since a lot of people dive Cow in backmount and if they went downstream toward the fault, they wouldn't be able to make it through all the restrictions in the upper portion of the tunnel.