Decide once and for all to trace it, and upon further 'head-sticking-underenath-vehicle' mode I saw this,

Either new pipe time or just blank the rear off completly this time and have done with it. Bah.
On a side note, after having fuel guage issues, and deciding on what to do, i notice the tank already has an extra wire. Saves me ajob at least, new screws and a clean up. Hopefully
