I've seen an
oil filter that was cut open after running 3000 miles with a magnet. There was an accumulation of iron paste on the inside opposite the magnet. Now whether the filter would have caught all that w/o the magnet in place is up for debate. The good strong ones that summit sells aren't cheap, but at least you know they can't do any harm, which is more than you say for many engine "improvements".
Z.