At the stealership a carbon clean will most likely consist of upper cylinder head cleaner sprayed into the intake manifold, letting it sit, starting the car and revving at 2500 RPM and spraying more into the intake manifold at short intervals. This should hopefully clean the small butterfly valves and the intake valves within the ports.
Upper cylinder head cleaner can also be sprayed before the throttle body to clean the throttle body itself.
I wouldn't worry too much about the MAF sensor as it sits behind the air filter and infront of any blow by oil. I took a look into myself the other day there is very minimal dirt/grim on it and mines a 2007, but is saying so, it doesn't hurt to give it a clean.