So my cars has been making with weird noise every time I go down a hill when I'm not even pressing the gas it also does it when I'm going at a good speed around 40 and I let go of the gas and when the car kinda goes into neutral and it sounds like a hissing crackling noise ?


I think it might be a bearing ? Or my Diverter valve ?

 

It only does it when I let go of the gas !

 

Assuming you have an A3 (since you posted in the A3 section) and assuming you have the 2.0t engine (since you mentioned diverter valve) - a damaged DV could be possible. Usually a bad DV will be followed by power loss and eventually CEL.

Does the car behave strange in anyway?

 

Not in any way it's only that noise it's making every time I stop pressing the gas or when I'm going down hill it's even makes it when I'm in parked and I rev the engine up to 4000rpm and when the rev comes down its make the hissing crackling noise

 

Well I would check the DV first - especially if you still have the original one. They weren't the greatest and most people already had a DV failure by now. Audi/VW have a revised version which holds more boost and lasts longer. Considering it's a relatively cheap and easy part to replace I would start there.