I have mine tucked back mate and much prefer it to them sticking out. Main reason being is that once the exhaust gets some heat into it it will expand and move out further from the valance. I had mine moved back because of this, as when I had been giving it some stick, the bloody thing nearly tripped me over
. It came a good 1 1/2" further out from the car than when cold.
I personally would leave it be, as once it's warmed up it will move out anyway
As for the staining, I have the same problem mate and have no idea how to get it off TBH..
Will keep an eye on this post to see if anyone has an answer, although I think it is more of a problem on CW cars TBH..