I also found with the LC header there is an issue with the factory exhaust manifold gasket and the header EGR passages. The gasket has a big hole for the exhaust and a small hole for the EGR port. The web of gasket between those two holes gets sooted up and blocks the gas flow. Also, I found the weld bead where the big tube is welded to the flange partially blocks that small passages as well. So I used a Dremel to grind down the weld beads a little then cut out the web of gasket material between the two holes to make a single large hole and that increased the EGR flow enough to drop my NOx readings enough to pass the CA smog test.