It is a mechanic convention to always refer to things with reference to the car, not the observer.Wen you speak of looking at the vacuum line, running off the manifold. heading left (towards the driver) this seems backwards if i am standing in front of the car at the grill and looking towards the windshield. Towards the driver would be "right', correct?
This is usually obvious except for 5-10% of things, such as the fact that the part of the dash board you look at is the rear of the dash, and you have to reach in front of it to get to the light bulbs, for example.
It gets even more interesting on transverse engines, as engine parts are referred to the engine, car parts to the chassis.
The hose Im thinking about comes out of the intake manifold, heads towards the rear of the car, then over to the left side of the car, towards the rear of the engine