Ok, so I've got 2000 a4 1.8t quattro 5 speed and I've put GIAC chip and the 710N recently.
After that, whenever I push hard on gas, around 4000rpm I hear some crackling or rattling noise (I would say plastic, not metal sound) and acceleration become weak. And it was getting worse over the time - acceleration almost got back to stock now. (Yes I know I need to get a boost gauge - may be next week).

So it sounded like a boost leak to me (may be some rubber tube ruptured after I've got bigger boost with the chip?) and I decided to do a boost leak test. I was following these instructions: http://forums.audiworld.com/a4/msgs/1659806.phtml

After starting to pressurize the system I could not hear any air leaks but the pressure would not go up!
Instead, all I could hear was some sort of bubbling and liquid dripping sound coming from somewhere below the turbo (may be oil bubbling in the oil pan?) This was weird!

So WTF was that? Please help, I'm loosing my mind.

 

Hey, so no one knows what can be wrong with my car?
Any ideas, please?

 

if it sounds like plastic and only happens under acceleration, I would bet that your dv is going bad. Get a 710n and that should help.

 

without knowing your vacuum level i couldn't make any recommendations since someone can only guess... u need to get that boost gauge!

 

he said he recently installed a 710n

 

Yep, I've got new 710n and it looks ok visually. Can it be n75?
The fact that I can't put any pressure into the system under the boost leak test (and I hear that liquid bubbling instead) is very strange to me. Looks like the air is going the wrong way somewhere...

 

me no read so good

 

it could be...

 

sorry ma man, me canno write so good either
me just likes to step on the gas, just tel me please woz wrong wiz ma car, me will be grateful