Looks like its been running well to me, looks a little on the rich side due to the carbon deposits, but thats normal on a turbo motor and one thats been ran for some time.
Combustion looks as if its been well under control, the area of no colouration is known as the squish area, you'll probably find that this ares of the cylinder head also has little carbon deposit build up.
On cylinders 2 & 3 at the bottom where there is also no colouration could well indicate that the piston is coming too close to the combustion chamber, this retards the ignition flame.