I really dont think the smell is from the tail pipe. From my wrx, you could smell
fuel from under the hood. It was a real evident smell.
From the factory, the wrx does run super rich. You can actually stick a blow torch behind the tail pipe on a wrx and watch it light up! (Dont try it too much).
Also, during cold AM startup, the car runs more fuel since the engine temps are very cold. In combination with my loose clamp, there was positive verification of fuel comming out of my line.
I dont think exaust gasses should be ruled out, but for those with the smell, you can really smell the gas in the cab and under the hood. Its very strong.
Yup...the yellow staining should not be there. Thats the gas. Promise.
If you go to home depot and spend about $10, buy a real long phillips and flat head screw driver. Keep it in the car in case you are in the middle of no where and the fuel starts comming out like crazy. Its a little cumbersome to get to, but you can use the flat head to spin the clamp around. Just take the
rubber intake hose off that connects to the filter box. You will have a good view of the screw from there.
I would tell the dealer about the staining. That way there is record that you reported something. This will probably help out much more if something does happen to the car before you can bring it in. Oh... just for the heck of it, buy a fire extinguisher.
Keep us up to date...