Xt660x 07 Vs Later models
 

I found that the 07 model has higher Kw specs than the other models, does this mean from 08 and later less performance?
07: 47.33 HP (34.5 kW) '14 47.34 HP (34.6 kW)
i know maybe is not all that big difference but i want to know just for knowledge reasons.

You wouldn't even feel that on the road, could simply be a revised part or different stock map that accounts for the difference.

Hi Vasillis,

The xt'07 is probably the best you can get. Because of surging complaints for the earlier models Yamaha have "upgraded" the '07 version with new ECU where last figures are 01-00 and it has a white paint dot. This ECU has a better mapping and almost eliminates all surging problems. Of course Kev's fuel mod will make it better but nevertheless the bike is the best edition with no O2 sensor.
Regarding the HP the 0,1 kW is nothing you can really feel as mentioned above. However a removed snorkel and DNA filter (a good Greek company) you will get real power feeling.
Try these.
I have got the '08 because (I think) looks better with the black wheels and forks, but would rather have the '07 without the O2 sensor. Even I am considering of changing the ECU and the wiring loom for the '07 version. Expensive though :D
My advise - go for the '07

Good luck