I got nearly the same behaviour, but I guess that's because I live at 2600 meters over the sea level. Where do you live bro? I guess I'll never be any higher than 130kmh at my hometown without any modification.Yesterday, my home town is pouring rain and i tried my bike to my limit. although my bike only just travel for 100 km (62 miles), but i risk it and tried as fast as i could. And it reach 132 km/h (82 Mph) at raining condition, at nite, on a semi freeway. Perhaps because it still new or i'm just afraid with the condition, it's easy to reach 120 km/h (74 mph) but then it get slow to reach 130 km/h (82 mph).
Could it be because the euro 2 type exhaust, or any other factor? i don't really know.
It accelerates smoothly till 120kmh and then it takes forever to go any further. I used to have a Hyosung 250 and it reaches 130kmh with no effort.