Engine Decoke as seen on Wheeler Dealers (Terraclean?)

[sulli]

Did anyone see the episode where Ed decoked the entire fuel system/engine apparently with a device that plugs into the fuel rail?

Assume there has been a previous post on this but the antiquated search facility didn't pick it up for me.

Anyway, anyone done, it? What are benefits/downsides? Thinking of doing it on my S4 to give the internals a spring clean - also got me thinking of the RS4 common issues of coking up that loses bih BHP and results in the need for head off decoking (£££)

[sulli]

I think because coke builds up regardless and isn't removed by normal servicing.