yes 12psi is the norm for our 4D56's. I used to have a boost controller on mine and I was at 17-18 psi for a while, no problems with it...just fuel consumption. I think 20psi is the line I would draw for being safe. at 18psi with my tiny little turbo it hauled ass....I couldn't shift gears quick enough. when I park my car for the winter I am going to take the boost controller off it and put it back on my pajero.