Does the idle settle when the engine warms up, ie once the coolant has burnt off. Another clue is which ever cylinder the coolant ends up in (normally #4) the spark plug will look as if its been steam cleaned!
If its a permanent rough idle it may be the stepper motor needs adjusting but that can't be done without involving a T4, TOAF might do it, I don't know. The stepper motor controls in idle air control valve, adjusts the idle depending on the load on the engine, lights, aircon etc. I bought a 1.8T a long time ago and it had a rough idle. Took it to Brian for a general once over and he'd never seen the stepper motor so far out of adjustment, reckoned it had never been adjusted from new! There is an adjusting screw (dunno where) but needs to T4 to set it within the correct parameters.
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