I am in agreement with Spooler. That manifold is only good if it is ported and polished. You would be better off doing a GTR manifold conversion. Just Spooler pointed out the issue is head gasket problems when you get above 18 psi which is long before the upper manifold becomes an issue. The oem manifold will start to fail at about 25 psi. My two cents, don't fix what's not broke!
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