[DayTE]

My mechanic uses a Carbon Clean system.

It has a wand that fits in just before the thottle body and cleans that. It also has another process that hooks in to the fuel lines that cleans the lines, the fuel rail and the back end of the injectors for a short period. The car is then started which uses the cleaning fluid to clean the rest of the injector and combustion chamber.

It's not the Wynns carbon clean system (they use a little bottle and something else), although it does a similiar thing to what the wynns one does this is much better and much more complete.

I did this to my car at only 30 000 kms and it made a hell of a difference, much smoother on/off throttle and revs a little cleaner.
Makes me think... I'm due to do it again!

I think the addatives do work a bit, but like everything they really need regular usage to get the best results.