Polo 9N 1.2 with misfire fault code 16556 VCDS

[Eugheugh]

I am getting a severe misfire about 30 odd seconds into a journey and last about 20 seconds before clearing completely. This only happens once in 20 odd trips in the car. Curiously the misfire disappears when I press the clutch pedal while revving or drop to a smaller gear (to reduce load). VCDS is showing 16556 fuel trim bank 1 PO172 - 35 - 10 system too rich intermittent. Some people have suggested the lambda sensor but Ross-Tech wiki is suggesting a number of other fuelling issues.

[Crasher]

I would replace the pre cat lambda sensor first, they are a life limited service component.