The 99-00 Busa are capable of 194mph.
Everything Japanese after that is limited to 186mph/300kph.
With the restrictions removed, an 01 to 07 Busa is also obviously capable of 194mph.
With restrictions removed an 08 to 14 Busa is capable of 197mph.
Keep in mind that this doesn't mean the bike will do that speed. Only with enough road(most likely over 1 mile), no head wind, good air temperature and humidity, elevation will change it, the rider's size and weight, ect. There are a lot of variables.
Stock gearing limits the bikes from going any faster. A gen2 needs a 41 tooth rear sprocket(stock is 43), or a 55 series rear tire(stock is a 50 series which is slightly shorter) to break 200mph. Again, that doesn't mean you can do 200mph.
The gen1 also needs taller gearing or tire, but it also needs more hp. The faster you go, the harder it is to continue to go faster.
The gen2's top speed limiter is removed along with the lower timing restrictions now in later versions of Ecu Editor(previously you could remove them separately). With the restrictions gone the gen2 is noticeably more aggressive at lower rpm's.
That's worth doing.