Inliners International Forums General Discussion Engines 250 intake/exhaust manifold install

I agree - center out. If possible get a tap or a good bolt and chase all the bolt holes cleaning them with some WD-40 as you go. Put them all in finger tight and tighten in about 3 steps.
The hot torque is because metal heats up and cools down differently. It is all cast iron but maybe the cylinder head has more Alloy than the intake/exhaust manifolds which are more pure cast iron. Plus they are hollow so transmit heat at a different rate.