Are you using spec-driven piping? Try using the route option "Axis/Edge/segment". When you choose "Extend" in your Route menu... pick the option "Csys/Axis"... then the sub-option mentioned above. You may have to setup a datum plane first, at the angle you want for the route... then select that during the routing as an angular reference for the segment.
Chris Benner
Autodesk ® Expert Elite