[27litres]

I still say that a regular inlet manifold solvent clean using Liqui-Moly inlet manifold cleaner, Subaru foaming inlet manifold cleaner or whatever other reputable products are in your market (Carby/Throttle Body cleaner or Brake Cleaner is too strong for this job, you need a dedicated product), is a good preventative maintenance procedure.
Do it at a minimum of every service, even in between services.

EGR coupled with PCV is what strangles inlet manifolds on direct injection cars. No manufacturer is spared, and it's not just the Germans who suffer from it.
Just look at what's happened to diesels since emissions standards necessitated EGR. 50,000 miles and their inlet manifolds are clogged with tar, and they struggle to run severely down on power.
Catch cans work for them, maybe that's another part solution for petrol too (though they're probably illegal for emissions)?

The virtues of FSI far outweigh it's drawback IMHO. High compression ratios and high pressure turbocharging are the immediate benefits, as well as cleaner emissions and lower fuel consumption (aka greater efficiency)
Mazda employ a 14:1 compression ratio on their Skyactiv petrol engines (and rate them for 91 RON).
VAG couple a 10:1 compression ratio with 24psi turbocharging on their TSI engines.
You couldn't achieve either of these without direct injection, and it's why the modern FSI engines are so powerful compared to their immediate predecessors (especially the small stuff) without an appreciable penalty in fuel consumption.