Mr Haynes says,- tighten in 4 stages 1, 18 ftlbs 2, 40 ftlbs 3, further 90 degress 4, further 90 degrees.
Me, I add a stage 2+ and tighten them to 60 before 90deg and 90 deg cos
it's running a fair bit of boost and I don't like blowing head gaskest.