What's the diffrence between Fuel Intake System Cleaning & De-Carbornization?

they are probably the same thing,you dont say what the vehicle is,but decokes(decarbonisation )was a cylinder head strip down to remove carbon deposits from the valves and ports.this is pretty m.uch ancient history as modern oils dont burn and leave the same crud behind.the most common thing that i can think of is the fuel injector nozzles can gum up which leads to poor atomisation and loss of power and economy.if not expensive probably worthwhile however you can buy a fuel additive which perform pretty much the same task