Not only is the output less at the wheels than the Audi 4.0 TFSI V8 and BMW S63TU V8 motors the Porsche design is outdated and inefficient. Mercedes-AMG themselves switched from a big 5.5 liter twin turbo V8 to a smaller and more efficient 4.0 liter top mount turbo M178 V8 design.
Porsche is following suit by ditching their old motor for a new smaller top mount design. We do not have the displacement figures but we would guess it also will be around 4.0 liters.
This engine is expected to find its way into various other VAG (Volkswagen Auto Group) vehicles including those from Bentley, Audi, and Lamborghini. It may end up being an Audi 4.0 TFSI V8 replacement.