Strange sounds after going off throttle

[4WDrifter]

I listened to your video

Check that your crankshaft pulley isn't split and that it is not hitting against the back surface of the intercooler.

I know this is a completely different tack to all that has been said so far but I had the same sort of noise and crankshaft pulley had split and the front part had moved forward to hit the back side of the intercooler (I have an S2) luckily no permanent damage done. I can't believe how lucky I was the get a second hand replacement pulley within an hour of posting on the wanted section. Put the car up on a lift, remove the drip tray and if the pulley looks okay then I'm sorry for wasting your time.

[minim]

PCV is the small cylindrical one that joins to the T hose under yhe inlet manifold it's not easily visible. The large diameter end points up I think check the Quattroworld FAQ. If you hear whooshing somewhere you clearly have a boost or vacuum hose issue somewhere. Does it idle ok as high idling and 561 dtc's is also sign of leaks.

That's the one I didn't replace. Will change that when I get back since I have to open that hose again to search for/install the missing fire guard that should be close to it.

There are no leaks in the intake system except that very little one in the ISV and if there are they have to be at a pressure over 1bar. I can't hear any leak from the ISV when applying 1bar pressure to the intake but I can spot it when spraying it with soapy water and waiting a bit so bubbles can accumulate but it's really small. Not showing instantly when spraying. Since it's so little I really doubt that this is causing the problem I got with the "steam train sound".

Incase there is a leak above 1 bar I would have to make myself another bung that fits the output from the turbo as I don't wan't to apply more pressure on the "pressure less" side of the turbo. Do you really think this much sound can be caused by a leak that's only showing from 1bar and up? Did you hear the sound on the video?

[Thecrispynoodle]

PCV is the small cylindrical one that joins to the T hose under yhe inlet manifold it's not easily visible. The large diameter end points up I think check the Quattroworld FAQ. If you hear whooshing somewhere you clearly have a boost or vacuum hose issue somewhere. Does it idle ok as high idling and 561 dtc's is also sign of leaks.

[minim]

By resirc valve do you mean the turbo bypass valve? Have you checked the PCV valve under the inlet manifold? Have checked correct orientation/operation of N75 valve?

I ment the valve that is resirculating air into the inlet hose right aftern the MAF when going off throttle. The aftermarket one that was in there was also mounted in the wrong orientation so it is like Audi made it now.

I did replace one valve down there but I don't think it was the PCV. It was the one way/non return valve that I swapped with a new one.

Noted your suggestion to check orientation/operation of N75. Thank you

[Thecrispynoodle]

By resirc valve do you mean the turbo bypass valve? Have you checked the PCV valve under the inlet manifold? Have checked correct orientation/operation of N75 valve?

[minim]

Short explained is that if I am at third gear and give wide open throttle at 3000rpm and leave the pedal or clutch out at 4000rpm I get this steam train (in lack of words) sound. I also feel that I might not have full power on third gear and up and it might be related to this. This happens if I keep going at third gear also so its not just happening when I increase 1krpm. I tried to get it on video even if it's not easy to hear anything trough a mobile camera and I will post the link below. The car is a RS2 -94

http://www.youtube.com/watch?v=-rd2cQuInGc&feature=youtu.be

I can't get to the car in the next two weeks so I'm just speculating in what could be wrong and will make myself a list of todo/thoughts/tests to do once I get back home.

Suggestions:
-check orientation and operation of N75 - By Thecrispynoodle
-check crank pulley to see if it's close/into the intercooler - By 4WDrifter
-check for heat shields or similar rubbing drivetrain - By Thecrispynoodle
-check rear diff mounts - By Thecrispynoodle

Todo:
- change small vacum hoses in the intake system. Changed the ones that was leaking but want all changed so I don't run into this problem with the ones that isn't changed yet.
- try to get a used ISV that is not leaking. Only a very little leak at it (1bar test) so I don't think this is related to my problems with the sound atleast. Could be causing problems with not giving me 100% power.
-try to find out what's causing the memory error code that vagcom is throwing. I dont' get other fault codes but that what all I had time to check. 65535 - Internal Control Module Memory Error

Tests:
-

Done:
-fixed airleaks in the intake system (except the isv mentioned above)
-new spark plugs
-changed from open filter to OEM filterbox+new filter
-new oem resirc valve



Since I've been googling like mad to figure out what could be wrong with my car I figured that putting it up here might give me some good hints. Can't really do much about it until I'm back from work but if you want to help out getting me in the right direction of what to look at I'll read up and be ready to go