Yes the Nikasil engines produce WAY more power than their Alusil counterpart, probably one if the reasons Nikasil isn't supposed to have the longevity.

I'm not sure if they mixed and matched the Alu/Nik engines or if they all came with Nik factory. I know that at first they were replacing the Niks with Niks cause they werent sure why the damage was happening but after the replacement Niks started coming back they cast new Alisil blocks and used them as replacements.