first of... sorry for hickjacking into this thread.. my question is. i went to mynismo website and they dont have nismo exhaust for the fx.. so the closest one to fit my fx would it be the Z exhaust?

Buddy you need to search a little bit first.. Really.. There were 3-4 similar posts in the last month JUST on this topic and the latest one is on the FX facts thread:
InfinitiScene.com - View Single Post - FX: Did You Know? (FX Facts)
2003-2008 FX35: The only true bolt-on aftermarket exhaust systems for the 35 are Stillen and HKS Legamax. Most other systems that fit a 350Z/G35 Coupe will fit FX35 but you'll need to get the tips extended and if the exhaust was originally made for 350Z, you'll need a G35 extension OR get the midpipe extended at a muffler shop.
edit: if the quoted one above is not clear enough, here's the answer:
Almost ALL 350Z, G35 aftermarket exhaust will fit FX35, BUT
1) 350Z exhaust will be short on the mid pipe and this either needs to get extended by the muffler shop OR you need to get the g35 extension
2) The tips will be short whether it's 350Z or G35 exhaust. These will need to get extended by the muffler shop as well
3) Even with these, there
might be fitment issues
4) Nismo is probably the most common one here. It is a 350Z exhaust. It's y-pipe WON'T fit AWD (almost no aftermarket y-pipes will fit except Kakumei), everything else will fit with the modifications explained above
5) Stillen and HKS Legamax for FX35 are the true bolt ons, no modifications needed
6) Stillen will have fitment issues for FX45, Nismo won't.