I have a similar problem, dont know if it is misfiring as i have never had a car misfire, and it is so intermittent that whenever i show anyone, nothing happens!!!
When booting the car mainly but when cruising too, it just seems really hesitant and jumps/splutters... I seem to only get 120 out of it too... this is wrong surely? (2.0 16v).
I have changed all the typical electronics (Leads, plugs, coil) used VAG-COM (nothing found) and it still occurs.
Is this the same problem?