Re: What pots and caps for p90s?
Tone control capacitor value: mostly a matter of taste because the curve when you turn down the pot changes irreversibly, and there isn't much change with the tone pot at "10" (unless you have a low value tone pot). I like 22nF over 47 nF in everything where I tested (didn't mess with 33 nF).
Tone control potentiometer: you get the exact same thing that you get with a 250 Kohm pot at "10" with a 500 Kohm pot turned down to where it measures 250 Kohm. There is no reason to use low values unless you never use it in the more open positions and you need finer graded control.
Volume potentiometer: I find 250 Kohm to be better only with vintage style Fender pickups, and very few exceptions like JBs.
So, 500/500/22 for almost everything, including P-90s for me.