My turbo issue

[Eggmond]

Hi every one
This is my 1st ever post so I hope someone could advise me...Firstly I have to admit I am a total novice re fixing cars anyway here goes I purchased a A4 2.0 FSI 2007 Cabriolet Auto last year and I love it........From getting the car I noticed when I accelerated and the auto box changed gear there was a loud wooshing noise from under the offside of the bonnet. The noise is louder if I accelerate harder. Oddly if I put the car into sports mode or change gear with the flappy paddles the noise is not as loud.
If I put the car into neutral and rev it sharply to 4000 revs and release the loud wooshing noise is there as well. The car drives well and there is ample power, I have checked my hoses and they appear fine. I took it to a mechanic who says the turbo could be faulty, but its been like this for a year........Any advice would be greatly appreciated
Regards
Eggmond

[Cavanmick]

It sounds like you have a split in a boost pipe, they can be hard to spot sometimes, either that or someone has fitted a dump valve to it

[Eggmond]

Mick
Thks for the reply def no dump valve on it. I take it the boost pipe must come from the turbo. Ive checked the ones on the nearside near the intercooler they are fine and the thick one that comes from the airbox on the offside that goes down to the turbo and that's ok, someone said it could be a boost pressure valve or switch??? so Ive ordered one of them cos it was only £22 but I'm worried it could be the turbo
Eggmond

[Cavanmick]

Highly unlikely it's the turbo, tye pipes you need to check are the thick ones coming from the turbo to the intercooler.does it do it when revving up or only when you release the throttle.

[Eggmond]

Mick it only does it after auto gear change when accelerating or after I release the throttle if i rev it whilst in neutral. Is the intercooler on the nearside and the turbo below the airbox on the offside if so I presume these pipes run across the front somewhere
Eggmond

[Cavanmick]

On the tdi (I'm presuming petrol is similar)it runs across the bottom of the radiator in a steel pipe but has rubber pipes at either end.

[Eggmond]

Thank you I will have a look today...that said it might be best for a mechanic to do it after the bank holiday

[Cavanmick]

Nothing you can't do yourself buddy, Jack the car up safely and follow the pipes as they route around the engine bay. It will only be on the pressure side ie after the turbo.

[Eggmond]

Well had the under tray off no leaks in the pipes I'm flummaxed now it must be a sensor or something like that, very strange. I'll have to get it to a mechanic and have them plug it into see if a fault shows up....it did have one 0088051(I believe may be wrong thou) when a friend did changed my oil but that didn't show up again when he rechecked it about an hour later, he did say that his machine was a cheap one and I may need to have it checked again with a VAG one (sorry guys that's way above my level of knowledge)