Alnico 6 is the darkest magnet I know. It has a very solid midrange/bass response without being as big and wooly as A8's.
I got mine from Addiction-FX a long time ago, and I can see that they're "out of stock" right now.Are those available?
Looking to make the upper mids in a P90 less pronounced.
p90's are strong in upper mids, that is part of their snarl.
But lowering the pickup also works a treat in general.