Very likely, yes. Carbon build-up on the intake valves is the price of direct injection, and a Mk5 2.0 FSI at 80k miles with a rough idle and cold-start misfires fits it exactly.
Why it happens: fuel is sprayed straight into the cylinder, so it never washes the back of the intake valves, and the oil vapour from the crankcase bakes onto them.
What you notice, usually at 60 to 100k miles:
- A rough or lumpy idle, a stumble, cold-start misfires.
- Loss of low-end power and throttle response.
- Misfire codes (the P0300 series) under load.
The fix is walnut blasting. I pull the intake manifold and media-blast the valves with crushed walnut shell through a vacuum shroud. It is the only real clean. Chemical intake cleaners do not touch carbon baked behind a closed valve.
I treat it as maintenance every 60 to 80k miles on a direct-injection GTI, not a one-off repair.
To slow the rate: a catch can cuts the oil vapour reaching the valves, and a healthy PCV matters, because a failed one dumps far more oil mist.
For the job you want walnut-blast media and new intake-manifold gaskets, plus a catch can if you want to slow it down.