So strange that a ecu reset does the job.
On a simalar note, i have a Pug 106 1.2 as a run around and that has had a lumpy feel to it and at higher speeds a missfire. I replaced plugs, airfilter, oil, new back box and checked for air leaks ect..... and it was miles better but not perfect
Last week i disconnected the battery over night, resetting the ecu and ever since the car drive's like new what a result.