the apexi N1 is just a cat back system. replaces stock from the downpipe back. if you want a system that includes a downpipe, then get a turbo back system.
try getting an uppipe too... it replaces the cat. before the turbo... which is a good thing (it really hurts performance being there and is prone to destroy the turbo)
in case you didnt know, when i say cat. it equals catalatyic converter (spell?)
hope this helps and happy modding!!