If youv'e got a CAT fitted I would say youve killed it as they run a a very high temp, if it all of a sudden got covered in snow! what happens is the outer casing contracts and crushes the core inside, making the CAT blocked, which is why you may have pressure coming back through the oil cap etc.
Or you have your tail pipe/box filled with frozen snow so the pressure cant get out.
VELVET BLUE UK INDIVIDUAL , IM THE LAST
UNITED WE STAND DIVIDED WE FALL
I stepped in a plate of Pasta the other day - now I have to worry about my Carbonara footprint!