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
My advise - go for the '07

Good luck

__________________
that is how i feel about my XTR
Mods so far:
Hyperpro front springs; Hyperpro rear shock spring; modified air box; LED tail light; LED indicators + new relay; YZ pegs; Lucas aluminum bar; brisk spark plug; snorkel removed; DNA stage 1; second hand DynoJet O2 mod; crash bars; front and rear steel braided brake lines; soft EBC brake pads; mitas 07 tyres, 2in1 Metal Mule exhaust, Blocked AIS, tall OEM screen, OTR bash plate