headers and exhaust

[Rufton]

Sorry, not much help but:

In reality, to many factors to easily estimate header performance.
Almost need a test track, trial and error runs, and full pocket.
When looking at headers for bike I was lucky that magazine ran tests of all the top headers vs stock.
Turns out stock was very good and the different headers tended to move curve around with no real average improvement.
Granted if you were racing near red line you could pick best but it would cost power on the low end.

You can use performance software to be pretty sure headers and exhaust pipe isn't too restrictive.