What kind of header are you talking about, Hotshot or OME, and what do you mean by primary and secondary? I decided to try and help since nobody is responding, but don't know that much ^_~
I believe the problems people have encountered are EGR lining up and 2nd O2 sensor being relocated. Stuff you can have a shop do or could do yourself with the right tools. Otherwise the flange should meet up. Mostly emmissions stuff. The 98' 200s will always mis-match in those areas. We're kind of the bastard child of sorts.
i have the hot shot header on right now, but i need to put a stock headerr back on for smogging. I just bought a header off of a 97 sentra. The is a pre-cat in this header tho.
__________________
Samson
Blood is thicker than water,
but cum is thichker than blood.