So...
I've been wondering about that 4.0 litre twin-turbo V8 diesel and whether it's the same as, or related to, the new V8 diesel in the SQ7 which features twin hot-side inside turbocharging boosted by an electric supercharger low down.
From what I can glean from the web thus far is that it isn't the same engine. It's still a 4 litre with hot vee charging but the two turbos are more traditionally mounted compared with those in the Audi SQ7.
In fact, having now gotten all intrigued, I have to point out that the turbo exhaust manifolding on the SQ7 V8 diesel is just nuts! To the point that it deserves a

and a

.
Each
valve - not cylinder - gets its own exhaust manifold outlet and this, in some bizarrely intricate, camshaft-determined trickery is how Audi arrives at "selective turbocharger actuation". Frisky.
The Porsche's 4 litre TT V8 diesel is comparatively more conventional from what I can see. And yet, in terms of outright outputs not far off at all from the Audi unit's figures being just 10 kW and 50 Nm down on the respective power and torque numbers. So that's pretty interesting in its own right.
As to how related the two engines are, say in terms of engine block, remains to be seen.