There is a plastic thingy on the end of the fuel rail. They crack and leak a small ammount of fuel onto the exhaust tubes going under the firewall. Almost impossable to see it. if you reach your hand under the intake on the back passenger side on the back of the fuel rail you will see this device and I bet if you run your engine for a few mins you can feel the gas spraying out of that thing. I dont remember what it is called but both my 94Runner and my father in laws 89Runner had this issues. Noone could figure it out. Matter of fact my 89' 4Runner burned up and it had the same gass smell issue. You might check into it.