My Diahatsu Terios 4WD 2006 SUVis giving me a gas fume smell inside the cabin.It happen only at times. When AC is switched off and open shutters it goes away. I replaced gas tank cap. Problem continue

SOURCE: gas smell

check for leaks in the fuel line from the gas tank up to the engine bay.the humming sound you hear at the back is your wheel bearing.it needs to be replaced.

SOURCE: Smell of gas fumes underneath vehicle near fuel tank

I also have a 2004 XC90 and a couple of months ago I had the exact same probelm... after multiple visits to my dealer's auto shop they figured out that it was the fuel pump. They replaced the fule pump and the smell disappeared. Good luck!

SOURCE: Strong odor of gasoline inside cabin

The is a short rubber hose in the the fuel line that connects to metal tubes on the driver side of the engine. When it is cold, the rubber shrinks, and if the clamps are loose, the fuel will leak from there. Tighten the clamps or replace the short hose with a hose that has some flex, a bit long, to accommodate the shrinkage movement. 
Good luck with the dealer, because when the engine heats up the hose the fuel does not leak at all. This was a recall on WRXs but even with the same setup, Subaru denies there is an issue in the 2.5 fuel line layout.  My dealer told me to call a tow truck when it happens again, no matter where or when, and bring it in?!?!?!

SOURCE: Gas Tank Leak?

I would look for a loose or ruptured fuel filler neck on the fuel tank, At the right height when 3/4 full

SOURCE: Smell of gas fumes underneath vehicle near fuel tank

this sounds like a gas pressure regulatur. a few minutes after starting,you start smelling fumes,and are getting bad gas mileage right?