Car has hardly been used since late last year, when the last real use was on a RR session where it pulled cleanly, fast forward 3 months, not even 200miles use and the car had developed a hesitation at 4000rpm+ under load, ie accelerating in 4th gear upwards. Did a few hours logging looing for misfires, signs of the ecu pulling the timing, boost etc etc, nothing obvious to be seen. Quick bit of research and S3's have had similar issues for a few years, cured by plugs/coilpacks, so bought some NGK iridium plugs, stuck them in yesterday and fault cured! Car running/pulling better than ever aswell.
Worh keeping an eye on, as the oem plugs looked fine when removed.