There is a difference between pinning and removing the butterflies regardless of the IMRC. There is more air going through the secondaries with the butterflies removed because of the rod has a slot in the middle for the butterfly. multiply the amount of air that can pass through the slot the butterfly goes in by 6 and that is the amount of overall additional air going into the secondary valve opening. It is additional metered air. You don't need dyno proof to understand this. Tis is also why people cut the Bar that holds the tb butterfly and report gains. The best way to do this mod is to remove the bar completely and do the IMRC spring mod. It tricks the IMRC int thinking it is still functioning.
