There's only a couple of FA20s in the UK, so doubtful if there's many been remapped. Edward at Xtreme does remote tunes for these though. Knock detection on these DIT engines is very comprehensive, so remap should be fairly straightforward. Limiting factor is the torque rating of the TR690 box. Have you been able to contact member samlux? He has a JDM FA20 Levorg, not sure if he's had a tune for UK fuel.