The Agera R has 1,140 horsepower and a theoretical top speed of 273 mph, but that hardly matters since you can't test it anywhere.
What you can do instead is go to Germany and try to get close to 220 mph on public roads using their unique Autobahn network. That's where a Jaguar XJ220 would give up the fight, and to think that the Koenigsegg has another fifty or so mph on tap at that point shows how much progress we made in the last two decades.
The boost? It's right where it belongs:
In a V8 flying in the fast lane.