to make 500 with a stock na head you would have to be using nitrous also because theres no way you are cramming enough boost through the 2.3 head. and if you were you would have thousands in engine management/turbo/intercooler/piping/ported manifolds,you get it? so why would you be using a stock head? I have been building 2.3 turbo motors for a while now and I dont know anyone making those kind of numbers with a stock n/a head