Hey dude they are speced to 6-8psi stock and there redline is about 6,800rpm for the intercooler piping i would go with 2.5" rather then 3" for better flow and faster compression slightly reducing lag also will make it a bit easier running the pipes to the intercooler at the front.
holden ppl are intimidated by my supra, on numerous occasions i've been in my supra with my window down talking with a holden nut, and they all want to know what my engine redline is, and before i answer they always look at the speedo and see that my reline is far higher then theres Then i add "not bad for a stroker engine"
what are holden 6 cylinders usually? there stroker engines too? or are they square or over square? whatever they are they sure can't rev high or smnoothly (probably an a V6 thing).