Hey guys, only new to the site hoping someone can help.

I have a 2006 Audi A3, when I accelerate and let off the accelerator around 2000 revs only (doesn't do it in very low rev or 2500 and up) I get a sound of a load of air being dumped somewhere, it's like a dump valve sound. This problem generally only happens when the car is warmed up.

When I rev the engine stationary it doesn't make the noise on the way up but on the way back down at 2000 it makes the sound again. The air type hissing sound

hope someone can help.

thanks in advance