"Subaru has confirmed to Autocar that there won’t be a turbocharged version or an all-wheel-drive BRZ and a convertible version has been ruled out."
"Power outputs, however, will differ with a Subaru-spec ECU liberating the BRZ’s power to “less than 300bhp,” compared with the FT-86’s 200bhp figure. "
Near 300hp out of a NA 2.0l is not going to happen with just ECU tuning.