did u mean exhaust? never heard of xhorst, any how the stock exhaust manifold should be able to handle the n1 cams haven't really heard of it not. as far as power im not sure. I did read somewhere you can get the sr16ve intake manifold and port it a certain size to ad a little horses.
Can it handle N1 cams? Yes! You would be fine until you got a proper manifold. It could even handle Kelfords, although it would not be ideal and would kill top-end power! A guy by me has the stock 20VE exhaust manifold with SR16VE cams and a 3" inch cat-back exhaust and the car pulls hard all the way up to 8000 RPM. He says he keeps the stock set-up for low-end torque purposes. He also has the stock SR20VE intake set-up as well (pipe and air box). A custom exhaust manifold would help it breath up top though and give him a better peak horsepower number.
SR16VE and SR20VE intake manifolds are the same! The N1 version is different.