if you put it straight thru your Intake manifold vaccum hose, it will clean the carbon buildup, out of the manifold, valves, pistons etc.

If you put it in your gas tank, it will clean the injectors

if you put it in your oil its supposed to free up stick valves.

I used to do it with every other oil change with my cars.. alot of people says it does bad things to cars.. But it never did anything bad for me on any of my cars one with 70k, all the way up to 230k.. only thing that happened to me was i flooded my Gt with it once..lol but it was my fault..