advanced engine technics

Many car engine manufactorers have many different approach to increase engine efficiency and maintain or even raise performance.
The main goals is to achieve the most perfect burning invironment, the least engine friction and the best possible termal efficiency.

The future is at piezo direct injection, solenoid intake and exhaust valves (rather than camshat), laser ignition (rather then spark plug) and of course electronic engine control.

Well piezo direct injection is allready the reality, laser ignition and solenoid valves will be reality from 5-8 years.

But at these point I will like to discuss about present technics.
VAG has FSI, which is solenoid/piezo direct injection engine with EGR and special intake plate so engine can operate under wery lean mixture at partial load.
BMW has valvetronic, whic is throttless engine, instead of it it has variabile camshaft timing and lift electronic control. The engine aslo comes with solenoid direct or manifold injection type.
Toyota, Honda uses VVTi, whic is also direct injection engine with variabile valve timing and lift electronic control.

There are also many more manufactorers with different tehnics.

But what is the essence of variabile valve timing and lift electronic control?
In simplification it is desire for valves to open later and shallower at low RPMs and sooner and deeper at high RPMs.

There are also some technics used to prevent swirling of the intake air in the intake system. If I am correct at low RPMs air travels at the longer tube that at high RPMs.

Turbos...
Many manufacorers proceed to small supercharged engines, because small engines use less fuel. These kind of engines have biturbo system - smaller for low RPMs and higher for high RPMs, so there are no turbo lag.

EGR..
this technic was used in the past only for turbos, but now all gasoline direct injection engines have it.
It is a bypass from exhaust manifold to intake manifold with electronic controled EGR valve and EGR cooler.
Engines before that used variabile valve timig and lift control to achiev EGR - exhaust valve didn't left all the exhaust gases out of the cylinder.

So do gasoline engines have all of these technics or just some of them?
(VAG's FSI for instance don't have variabile valve timing and lift control)
Why diesel engines don't have variabile valve timing and lift control?