2k exhaust improvements?

I have the non-cal package (2 o2 sensors and 1 cat in the tailpipe) nothing in the downtube. Is there any benefit to a header?

I'd personally say the marginal improvement in HP is not worth the cost....but, if you need a new one anyway, then why not.

The dollar cost of any performance improvement from a 00-01 header is pretty significant. The 00-01 cast iron manifold is unlikely to crack. You will likely have better performance results per dollar spent installing a high flow cat and catback exhaust.