Since i'm going to AutoX tomorrow, i took out the rear trunk mat and everything that is in the trunk.Weirdly, there was loud hissing sound coming from the rear right inside the trunk. Is this normal? It's especially loud when idling. Don't think i have any problem in my car..

 

Do you have Bose in your Z? if so, could it be the amp powering up, not really sure otherwise.

 

no Bose. It's the hissing sound that you hear when you install jwt popcharger or plenum spacer.
I installed homedepot oil can and thr hissing sound is the same as comin from the rear. Rear makes more loud and consistent flowing of hissing sound though.
maybe coming from the exhaust inside?

 

fuel pump maybe.