Age old question!

[vc-10]

The advantage of direct injection isn't so much when you're flooring it, and want 100% of the O2 in the air to be combusted to get maximum power, but when you're on a light throttle. During this time the engine will operate in a 'stratified charge' mode (hence T(F)SI- Turbo (Fuel) Stratified Injection!), where the direct injection allows a small ring of fuel, with only part of the air in the cylinder being burnt as only part of it has fuel in it. This allows for lean burn but without the high NOx emissions (ha!) of a traditional lean burn, where the air/fuel mixture was even but with a significant excess of air.

Under hard acceleration, a direct injected engine will be burning the same ratio of air and fuel as a traditional port injection engine. They save fuel when you're on part throttle, where the engine can open the throttle valve more, but keep burning fuel in a smaller portion of the cylinder at the stoichiometric ratio of 14.64:1, which combusts all the fuel and all the O2 in the mix.

This is also how these TSI/FSI engines can give you a great MPG when you're cruising along at a gentle 60 mph, but aren't so impressive when the engine is having to work hard. As someone once described the Ford EcoBoost engines- you can have Eco, or Boost, but not both at the same time.

So if you have a nice shiny new 6C GTI, then this is a great excuse to enjoy all 192PS it has to offer! Although I'm not sure if 'I'm trying to prevent buildup on my intake valves, officer' is going to hold up in court.