As a test, how about the OEM header, extrude honed and then an ID and OD coating?

That would an interesting comparision during a dyno day.
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Explain the extrude honing process and if possible where to get it done, please. I'm up for the test Andy. I'll provide the header and dyno time. You provide the extrude honing and coating. :P

Also, what are advantages to internal coating?

R