If your just going with a sfmu you deff. should not run that large injectors. When I did the sfmu route I used 440cc and the fuel pressure was down to around 16-18 psi, i dont remember exactly it was along time ago. But Id recommend something smaller than the basic dsm 450injectors somewhere around 380's and this is only for stock motor setup on low boost. And you can still run them on Megasquirt but if you build the motor or is it built? and run High boost Then you'll need to up the injector size.