Why wasn't the jetting changed when the 2.5" system was showing rich. The engine appeared to like the open header A/F ratio. Kind of invalidates any comparison.
Two things come to mind with your statement.
1; You don't always see or hear them say they did "***" to the engine since they are time limited. Not to mention making every mention of every little thing is boring and tedious.
2; Even if they did not, the jet change is small potatoes in the grand scheme of things. There not getting back the lost power.
I do not consider it an invalidated test.