When i rev it hard or gas on it, i have this blowoff value sound. Im thinking it's the timing belt that's slipping, but im not sure?
ANyone hae any advice? or happened to them before?

i drive an is300 2001 with 130 000km.

 

I would think drive belt before timing belt. If you're timing belt was slipping that bad you're car would more than likely not be running

Also check the tensioners on the drive belt. When those bearings go they sqeal like a banshee!

 

bumppp !!!!!!!!!

 

To reiterate, chances are very good your accessory drive belts are in need of replacement, based of the information provided....."Blowoff value sound" is new to me ! Timing belts have cogs to prevent slipping, accessory belts do not..