I am re-doing a bathroom and there is a 10" fur down above where the sink is going. I think its because of the vent coming up from the sink. It stays inside the wall and then It makes 2 90's (s shaped) to go around the top plate. I really want to raise the fur down to fit a nicer light fixture above the mirror. Any ideas?

if you have the room under the pipe just raise it, if you have to cut the pipe see if you can do a 45 right below the top plate then the tie in above the plate, you can notch the bottom plate about 2 1/2" deep to accommodate the 45. this will create room to do pretty much what you want to, will still need a furr down of about 4" though.

Just hole drill the top plate. If it is two large a pipe just use a reducer to get through the top plate then you can use another flange to increase the pipe size once in the attic. We got rid or our fur downs completely on both our vanities and it works just fine - all it is doing is just providing air behind water so I wasn't worried about reducing it the 6 inches or so to get through my top plate.

If you can see into the attic and from the top of the wall to the roof deck and you have enough room...
If the pipe below the top plates is 1 1/2" or 2" cut the pipe below the plate and drill a large enough hole to put the pipe thru. Put a coupling on the pipe you cut off and add a piece long enough to stick up above the top plate 1". You can put a 90 degree elbow on it and run your vent back to the stack out the roof.
If the vent is a 3" or 4" vent you will have to do it like Hop described.

Thanks guys. It is a 3 in pipe all the way to the stack. The fur down needs to be right at the bottom of the plate. This bathroom has a little build out and the slope of the roof makes it even more fun. I'm thinking I will probably do a combo of everything....reduce it down a little, make a 45 and notch the top plate to take it back to the stack, then I can use the same hole and just change the stack to the smaller size on the roof.
Good stuff here!

Worked out good. Just got two reducers, 3 "to 1.5". Reduced down, made the notch and used the second to take it back to 3". The toilets gurgled for a day but seems to be fine now...probably just a change in air flow.

I hate fur downs. I just finished remodeling my U shaped kitchen and master bath and tore out all the fur downs and they exposed the attic and the insulation had to be replaced after new drywall was put back. I have one bathroom left to do in the future and I am seriously thinking about leaving it.