its a 2004 audi a4 1.8t and it ONLY "whistles" at 2000 rpms, not any higher, not any lower.

The whistle sounds like air going through a metal tube or something, it is the most annoying sound ever.

I got an oil change 5k miles ago but didn't really do much. any idea?

Could it possibly be that the turbo kicks in at 2 grand?

Lacking power? You might have a vacuum leak causing the whistle and it's only audible at 2k~ rpm.

If you had a turbo going bad it'd sound like a dentist drill. Not like a whistle. A good K03 is pretty damned quiet.

Well unless your turbo ONLY works at 2,000 rpms and not any higher or any lower makes your attempt to make adsquare look stupid is an EPIC FAIL

Theres a very important part of reading and thats "Comprehension".

Also as stated, Vacuum leaks cannot occur at 2,000 rpms due to the lack of vacuum off idle.

Now my question is does it occur when the car is sitting at 2,000 rpms or when driving around 2,000 rpms...? (Under Load)

ok well it could be 1 of 2 things
first ... when does the 1.8t go into pressure? if its at 2k the its prob a boost leak ... pull all the pipe twist it around and such look for tears or cracks ...mine sounded like a whistle at first then it was sounded like a pissed off blowdryer haha

seconds those little tubes that run from the intake box to the fresh air source the lil bit of foam that helps the seal could be bad ... causing a whistle.. maybe idk Im not looking at the car so it could be a number of things

I had some exhaust problems and now mine is whistling also. I haven't had the time to check it out yet, but I guess a leak is a possible cause.

FWIW, I had a "whistling" sound at idle but couldn't find the source for quite a while. Turned out that the rubber elbow on the EGR system had hardened from heat/age and cracked. (On my 00 1.8 A4, pass side of motor has 2 metal tubes running along the valve cover above the exhaust mani. There are rubber elbows that come off the front of these tubes, and the one closest to the exhaust was the culprit.) Whistle is gone with its replacement.

I seem to be one of the few readers fortunate enough to have a GREAT local Audi dealership, thanks to their parts desk. When I went down to pick up the elbow, my contact on the parts desk suggested following that system around the back of the motor and to the block under the intake manifold. He said a failure of the elbow typically came at the same time as failure of other pieces on that system. Sure enough, the EGR valve, the "Y" shaped vacuum boost, and the breather pipe (looks like a "7" and is very close to the block) were all stuffed. The breather pipe was choked w sludge/carbon and the vacuum boost was seperated, with the two halves just sitting together. (Amazing that the car was running at all!) The car runs significantly better now..and still no whistle.

to adsquare:

did your problem ever get solved? what was it? i think i have the same issue. there are several possible solutions to your "whistle" but you never gave us "the money shot." did you ever fix it, and if so what was it?

it's driving me nuts. how much $ am i looking at?

I have had some similar problems. I hear this whistling or loud NAAAAAAAAAA sound at higher RPMs, usually 2.5K and above. At first I thought this was the turbo too since the problem was in synergy with when the turbo when on for accelerating and downshift accelerating. Now I have a different opinion. My check engine light came on the other day and read back code P1176, I was told this means either Rear O2 Sensor failure or Catalytic Converter failure. Given the fact my A4 is 10 years old and has 110K miles on it I wouldn't be surprised. But my thoughts are that its possible the catalytic converter is the problem becuase sometimes the turbo goes on without the noise at all, but when the noise does happen, the turbo kicks on and I hear nothing for the first 5 seconds, then I start hearing the noise. Makes me think its something on the back end and exhaust system since there is a delay on the noise. I have no idea if it could be this vacuum seal valve clogged stuff, its possible, but I dont know. Im just more sure its not the turbo itself.