Metal attracted to the super powerful inner filter magnets.  These metal particles were removed from a NEW blown, 1000HP, 572BBC.  These pictures were taken after several dyno "break in" pulls.

Metal particles found on the magnets (in the filter) can often warn of premature engine failure.  We once found a piece of valve spring on a magnet and replaced the bad part before any valve train problems occurred!    Magnets can be checked in a matter of minutes.  Even if the filter cartridges are not being replaced.