I was told that the previous owner detuned it when it had the original TD04, then put the VF39 in, replaced the vacuum lines as well as removed the restrictor pill so that it would only run at wastegate pressure, then had it retuned for the VF39.
I find that highly unlikely, especially considering that there's no reason to tune a car to run spring pressure.. you can just plumb the vacuum line on the wastegate directly to the nipple on the compressor outlet and it will run wastegate pressure, no tuning needed. It's far more likely that the car was having serious issues which put it into limp mode, making it run wastegate pressure.. so he decided to make it someone else's problem rather than trying to fix it.
I would take the car to a reputable Subaru shop with a tuner and have it looked over.. I'm willing to bet there's no tune on it at all. Hopefully nothing is damaged beyond repair.