Is this normal for a 1996 Disco?

[GTDisco]

I have a 1996 Disco and noticed that when my truck is on, this hose gets compressed. It's as if the suction that goes through it makes it collapse or suck into itself. Is this normal? Does this affect the performance? Do I need to replace it? What causes this to happen? Thanks for the help.

 

[joey]

You need a new hose... or your PVC is clogged, basically that is what it is that the hose goes too in the valve cover.