Have bought a 2004 1.2 fabia. When cold the revs are a bit boggy. Engine light is on. When it starts getting to temp a high pitched whistle starts. Clutch in or out brakes pressed or not and steering doesn't make a difference. When driving speeding up it stops but comes back when idle. I'm thinking it is a vacuum hose but I can't for the life find it. Please help. 

The vacuum hose runs from the brake servo to the inlet plenum, there is a non-return valve and there are a number of joints, all of which can and will split, just looking won't find the problem you must try and pull each joint to find the split.

I have found the hose under the massive air filter but there is no valve or joints. It goes from the master cylinder in the the throttle body. Should it run along the bulk head?