We run the FP 3794 on our "Mexico" STi. It's a 2011 STi (owner lives in Mexico) and he made 709whp at on 34.5psi on C16 fuel.
We recently swapped this turbo out for a BorgWarner s300sx3 turbo for better times in the 1/4 mile (we are keeping the FP 3794 for the Texas Mile in March). We made 675whp at 32psi on E85 on this set-up. We like the BW alot but will be putting the FP 3794 back on around February when we starting getting ready to break 800whp for the Texas Mile.