J-L A4

Hi,

Since a got this Audi A4 2010 manual, I have a power lag passing 3000 RPM with every speed.
I upgrade to Stage 1+ to help the low torque and mayby remove the lag but it change nothing.
I recently change the air filter for a cold air and a boost gauge as a second try and the lag didn't change but now there is a loud annoying whistling sound.

The original air box damper the sound that I heard now but the sound and the power lag match perfectly

By reading the boost gauge, I see that the lag happen between 0 to 5 psi, not following any engine rev speed. The pressure pass from vaccum to 0, freeze a moment and whistle sound happen at the same time until I pass 5 psi and then go full acceleration. The whistle seem to be the cause of the lag, like a vibrating part inside a valve

The problem is worst in traffic or normal cruising because it is always in the range of 0 to 5 psi.

What I know and try:
-Got 1 check engine for "Over boost" because the pressure didn't go down fast enough after reaching the peak pressure
-Try to unplug the diverter valve, no change
-Change the end of the diverter valve by a replecement kit with brass piston and rubber seal, no change but better respond and no leak at high boost
-Try again to unplug the diverter valve, no change
-Do a static leak test, no leak and go up to 25 psi
-PCV valve change 2 times by Audi for oil consuption
-Brand new turbo on warranty du to wasgate defect
-Block the PCV valve connection to the turbo inlet, change the sound but power loss and other new sounds
-Block the PCV valve connection to the intake manifold, no change
-Before changing the air filter, there was a small whistle that I heard when driving side to wall
-Try going back to stage 1 and stock, no change (ECS stage 1 and 1+)
-The whistle sound is almost the same as a rescue whistle (like camping stuff)
-Audi just answer me as always "Your car is normal"
-2 others garages didn't find anything
-It is not the sound of a worn out bushing sleeve
-It is not the sound of a defective PCV valve (test with the oil cap)

The only test that do something is seems related to the PCV valve but it is the third one and I don't have any other clue of problem with this valve.

Does this car naturally whistle or there is really a defective part?
What other test can be done?

Sorry for my english, I am french canadian...

thanks for any help

zainag

I have a stock 2017 B9 A4 and I get the whistle at around that boost as well. Its faint and at this point I'm thinking that its likely normal - unless someone tells me that its not. I've just gone over 1000 miles so I'm not sure if it will eventually go away or if it's indicative of a larger issue.

J-L A4

Yes I got the same conclusuon that audi part have big design flaw and that they don't replace them. But it is not physicaly normal so there is a part that is not working well and can be improve.

I already found 3 valves that were leaking air as build. By replacing them I get more power and best fuel consumption. If I can found the last leaking valve it will be a big bonus.

The sound is worst with the cold temperature coming so I continue to investigate