If that's what you believe that's fine - I changed from Shoenfeld 1.75 TO Shoenfeld 1.75 stepped to 1.875 headers and lost .05 ET. That's computer corrected to the weather and stepped headers were coated. Now that's nothing to feel but never the less a loss.
A change in ET is irrelevant. Trap speed is the direct indicator of your power:weight ratio. Elapsed time is merely an indicator of your traction at that exact power level.
Tell us how your trap speed changed (be sure to include all relevant weather readouts, including measured altitude density, on both runs) and we can decide if you actually lost or gained anything by your header change.