I ve a 4 yr old 2.0 petrol FSI GT.

Twice in recent months when engine's been cold, it's taken a lot of turning over, then it's been very reluctant to get going.
The last time it took say 5-6+ seconds of starting, finally caught, but really felt bogged down and rough. Took a few more seconds to get going only after giving it a bit of throttle. Felt like it had a misfire

Then all of its own accord rose to 3500 revs and stuck there. Quite a lot of smoke too.

The revs then gradually fell. Slightly embarrassed in the car park to have the car revving its nuts off!

Fine once again this morning.

Anyone got any ideas what this might be or had this happen too?

An auto express and a telegraph article both suggest it's possibly due to using low octane petrol. Hopefully it is just me being a cheapskate, I might give the high octane stuff a go - hopefully that's the case! Anyone found it helps?