Yeah, the company that can remove the speed "governor" is Mazda
And if some aftermarket outfit like Superchips or whoever finally cracks it, the techies on this board will be all over it!
Just looked up info on engine availability and top speed for the 2005 Euro spec Mazda 6. In gas engines there's a 1.8, 2.0, 2.3, and two 2.0 litre diesels (a 121hp and 136 hp version) with 3 body styles and AWD available on the wagon. The most powerful engine (the 2.3 gas) produces 166 hp @ 6500 rpm and has a listed top speed of 133 mph on the 4-door/5-spd mtx (the lightest body style). This is the fastest one I see on Mazda's UK website. I don't know about the German site, but the specs should
be the same. Of course the 3.0 Duratec is not currently available there at all.
Anyhow, even with a measly 160hp or so, a 2.3 litre car will, given sufficient time, get up to 130mph+ I'm sure. I don't know about 143mph....that's a bit of a stretch I'd say, although these puppies have a pretty low drag coefficient after all. This is purely speculation, but I'd guess an ungoverned
Mazda 6s with the 3.0 Duratec in the most favorable conditions would be good to 145 or so.