Boost cuts out at 3000 rpm in 4th gear and sounds like i've got a dump valve!
I've been having increasing trouble with my 110hp A3 tdi loosing power on the motorway recently. It only ever does it in 4th gear and at around 3000 rpm. It's just like it goes into limp mode and i have no boost until i switch the engine off and back on again, then it's back to normal.
I also noticed today that if i rev my engine, when the revs drop down it sounds like i've got a dump valve! It sounds like a chatter-type dump valve. So i'm thinking i've got a pipe loose or split somewhere? It also shakes quite abit when the revs drop back down and sometimes my idle isn't very smooth.
I've done a lot of research on this and i think i can rule out the maf sensor. Could it be n75 valve related? I have looked for it on my engine but cant find it. I think my engine code is ASV. Any advice would be much appreciated