[gpvecchi]

THIS IS JUST MY PERSONAL OPINION: I didn't try the ACE Header, but I saw many dynos that shows that ACE is not a miracle, especially if used with high octane fuel.
In Japan, nobody uses ACE, but HKS or Fujitsubo (the new EPU exhaust with EL long pipes).
On paper, 42.7 mm long primaries should give more torque at low rpms, but sacrifying high rpms against 45 mm of the 2017 headers. Very long secondaries should give good mid range torque.
With ACE, I expect a little more on high rpms, but not as much any classic EL header, almost same low end torque of stock >2017 header and almost no mid range torque hole.
Does this justify the cost? In my opinion, no.