Infinitely variable valve actuation would eliminate the need for a throttle blade.
This would eliminate part throttle pumping losses and result in improved part throttle fuel economy. ( note that about half of the diesel fuel economy advantage is due to this, the other half is due to diesel fuel having more energy per gallon).
Now if we could just get it to use less energy than a camshaft and if we could just control it as we needed and if we could just make it cheap enough...