Its something in the new FPR setup Subaru switched to in 08. Actually a common issue, not sure why your tuner isn't aware of it. The MECHANICAL (proper) fix is to upgrade your FPR and ditch the stock balancing hoses and other junk they put in. You can also swap in an OEM FPR setup from earlier year STIs (04-07 STI) if you want to keep stock setup. You'll need the FPR and lines running to and from your fuel rails to do the swap.