I asked this question both here and on se-r.net. Both with no responses. So I did a little research on my own (what I should have done from the start) and thought I would post what I found for future reference. The primera tubular exhaust manifold is made of stainless steel and flows better than the us spec cast manifold, but not as well as a hotshot or stillen header. To make this work you would have to figure out a way to incorperate the O2 sensor into the manifold. I have talked with a few people who said the best way to do that would be to have someone experienced in welding stainless steel to build up a spot to drill and tap for the sensor. The next problem is the pipe that goes from the exhaust manifold to the rest of the exhaust. The best sounding solution to me is to cut the flange off of the stock pipe, cut a few inches out of the pipe and weld the flange back on. After finding all of this out I have decided not to use the primera manifold on my car because by the time I buy the manifold, pay someone to weld for the O2 sensor, cut and weld the downpipe, and then put it all on, it will probably cost 200 dollars anyway, save another 150 and you have a hotshot header with a lot less hassels. Just my 2 cents.