The Swedish company BSR (bsr.se) have now been able to trim the 1.2 81kW engine. They quote 131HP (stock 110) and 234 NM of torque (stock 175) after tuning. This is a proper engine tuning, not a plugin box.

Thanks - Keeping an eye on 1.2 TSi 16v remap developments... although the 1.2 seems OK at 70-80 on the motorway it does seem a little more torque would not go amiss. A 1.4 ACT DSG 2WD or 4WD would IMHO be the best Yeti drivetrain.  

I have also found another option - German RaceChip Pro2, a plugin chip. They also promise similar improvements. I might go for this one, as it is possible to easily revert back to stock. 

http://www.racechip.com/racechip-pro2/