With the P90, did you try adjusting the pickup height? That has a lot to do with the sound. Not easy on a dog-ear as you need to use a different height cover and bend the metal mounting ears to suit, which isn't always easy. But it is a definite way of tuning the sound.

Vintage style wiring also helps, where the tone control is taken from the volume pot output, not the input. You can then turn down the volume without loosing treble and get a lot more clarity.