I'm about to switch from a Scotts Rod 3" system to the Redback 2.5" system - advice from Redback suggests that I might lose 3kW up top (where I don't need it) and pick up a few Newton metres in the midrange, where I do need it.
If I can, I'll get a dyno tune before and after and post results. I am running a Steinbauer chip, currently set to 120%.