The exhaust manifold you have can't be stock, because stock is side exhaust and the o.s. is rear exhaust
It will come with a new exhaust manifold, but be sure the pipe you end up getting is made for rear exhaust. They might say the pipe is for rs4, but that is for a stock motor with side exhaust.
The skyline pipe that Kamikaze said is rear exhaust so if you but that one you will be fine