The intake and the exhaust minus header are legit. I bought my car brand new with them already installed. You should be good to that point anyway as far as under the hood goes. The Nismo header is a 'no-go' in terms of street use though. That's regardless of the pre-cat or not. The one with the cat might fool someone at first glance if you want to be cosmetic. I just figure since it's illegal in either case, I'm going with the header without the cat.
I WORK AT CERRITOS NISSAN. NISMO CAI IS NOT LEGAL. IT IS A R-TUNE PRODUCT. HOW EVER IF YOU NEED ONE I CAN GET YOU INJEN. IT IS LEGAL. A NISMO EXHAUST IS LEGAL. ALMOST ALL EXHAUST ARE LEGAL BECAUSE THEY ARE AFTER THE EMISSIONS AND WILL NOT ALTER IT. THE ONLY THING THAT MAKES AN EXHAUST ILLEGAL IS THE NOISE. MOST HEADERS ARE ILLEGAL. VERY FEW COMPANYS WILL MAKE LEGAL HEADERS YOU HAVE TO LOOK