I wouldn't go past 12psi with the stock turbo, but that's just me. I've no idea what type of boost is actually safe to run with it. Myself, I'd try to find a turbo with about a .85 A/R for lots of high-end, that you don't have to completely mash the throttle to get. That way it's still fun on the road, but you get good power and response on the track. I really know nothing about the 57 trim ct26, I just thought I'd throw in my thoughts.