I had experienced a strong gas smell entering the cabin of my 1995 Quest usually when cold and running the heater or defroster. The smell would eventually disappear once the engine had warmed up. I came here and read several posts suggesting replacing the fuel rail rubber hoses or tightening up the screws on the clamps. The gas vapour leaks out of these ends when cold and if not snug. I inspected the hoses and they looked fine and I tightened the clamps' screws (all were somewhat loose). And yes, they were hard to get to! I THOUGHT I had tightened all the clamps but the gas smell continued as before. Finally after a few weeks of this driving me crazy, I took another look under the hood and realized there was one more hidden clamp which I missed and it was quite loose. I tightened that up and the gas smell is now gone!
Here's a photo showing the screw locations. Sorry I couldn't get a better shot. As I said, it was tough to get in there with a screwdriver. Hope this is helpful to you.