On my truck there seemed to be zero difference between tow-performance-extreme, in fact, the tow setting seemed to run the best.
Throttle response was so "smooth" that you could barely tell there was any additional power below 1/2 to 3/4 throttle.
I want something to get my SPS66 spooling quicker from 0-12psi, an area where this turbo is particularly laggy. After that, though, look out! Here comes boost!
I might have to break down and buy another one to check it out. I wish they'd do a Crazy Larry for the SO/HO trucks as well.