Full Flow On An Assembled Engine???

I ran across this and it looks sketchy.

http://www.dune-buggy.com/techtips/fullflow/

What do you guys think?

i stopped reading at 300psi, thats a little over the top.
if you had 300 psi blowing filters is not the problem but shooting plugs and maybe pump bolts would do same nasty damage.

yeah done it like that before

I was worried about metal shavings.