Matching is the key....

You dont want hogged out head intake/exhaust ports.. You dont want your heads ported to the max if you have a dinky cam/cams.
Head flow numbers are a good way of getting an idea of the performance of the head but velocity is often over looked as being an important factor.

I dont believe anything should be broken in hard...
It makes no sense to me. And it makes no sense to car manufactures who put 10 year warranties on there car who recommend a gentle break in period.