Which is the fourth fastest production car in the world?

It depends how you measure that. But by top speed it is Saleen S7 Twin-Turbo ( Top-10-list.org) with 248 mph and if measure by acceleration it is bugatti veyron http://thefastestcars.net/top-fastest-cars-in-the-world/top-10-fastest-cars-in-the-world.htm