Most of the saw racers use heavily modified chain...it has had much of the cutters remove, nearly to the back of the cutter. Since most chain tapers to the back, the kerf gets narrower as you gp back. As well, some like to remove a bit from the side of the cutter to narrow the cutter even more, so there is even more of an effect. Finally, chain in the sharp pointy square tooth chisel form is the preferred type.
I don't think there is any full chisel narrow-kerf out there. Interesting thought, though...I've got a little Jonsered with a 20" bar and narrow-kerf .325...little 50cc saw should be pretty overtaxed at 20", but with the 95vp chain, it isn't so bad. I admit I'm only comfortable with a 16" bar on it, though.