Originally Posted by airudah2000
Update: The noise came back after a few days. I noticed it stops once i've driven for about 20 minuites. It usually occurs on cold starts or if i havent driven for about 3 days.
As I said in my last post, this sounds like it could be partially blocked injectors. Depending on how clogged they are, they should be cleanable in-situ by the use of a high-pressure solvent rig. The reason why the noise diminishes after you floor the throttle is that you're increasing the fuel pressure, which has a similar, albeit reduced and temporary, effect to high-pressure cleaning.
How many miles do you have on the car and what sort of driving do you normally do?