The second calculator down on this page can help you determine which size injectors you need to achieve your horsepower goals.
http://www.rceng.com/technical.aspx
I calculated 22.5 lb per hour injectors to get 250 crank horsepower at a safe 80% duty cycle. You should note that our cars have about 58 psi fuel pressure.
Also, I pulled this off another thread. This is the injector other mercedes 3.2's run