Disca said:This was a heavily debated topic within the S5 forums as the V8 was known to coke up.
I had the S5 cleaned by a competitor to Terraclean, http://www.enginecarbonclean.com/, which basically just pumps hydrogen into the air intake while running that burns off the carbon. Results were definitely noticeable and I think I even documented them on here. Shall try find them.
This is slightly different to terraclean. That will clean the intake side of the valves, Terraclean runs in through the fuel system.