The way the injector works is it is supplied with a certain pressure of fuel. The coil opens up and allows the fuel to be sprayed into the engine. The coil doesn't push more fuel or less fuel. It just opens up. The thing that allows more fuel to be injected is the duration of the open cycle. When at idle a 555 might run only 3% duration or so. At WOT on my car the duration goes to 95-100% duration at 19-20psi. The coil doesn't know what the pressure is, it just knows how long to stay open. As far as 600 rwhp, it can be done on 555's with the right fuel and big turbos and an intercooler. But this is just my opinion....
A.K.A. "THE BACKROAD BANDIT"........ THE ONLY SPEED LIMIT IS 'c'