Man, this raises a long-standing question for me. I bought a brand new MIM P bass from GC out in El Cerrito, CA in '95, and it was my first bass. A guitar and bass playing friend helped me pick it out from the eight or so that they had.
Found a good playing basic white/rosewood one (on sale for $239, as I recall) and started to practice. Took the bass to my same friend's studio and he and everyone else there were liking the cool vintage (their description) sound of my bass. My friend even used the bass to record a couple of reggae style songs he was recording. I left it stock except for a Schaller bridge that I put on it.
A few years later I found a good deal on a 1968 Telecaster bass neck in great shape (which I really like 'cause I have big hands), and I put it on that MIM body. I thought that I had better upgrade the pickup at the same time, and I put in some Fender '62 reissues in it. I left the rest of the pots and wiring original MIM stock. The '62 RI pickups were fine, but had a lot more high end and were more clanky, so I had to compensate for this by adjusting the tone knob on the bass and my amp, and I didn't like that sound as much as the original pickups with the bass tone full open and the amp set more flat. It seemed that having to turn down the treble on my amp, I lost a lot of my midrange presence, so to speak. So I put the original MIM pickups back in, turned my treble back up to 'flat' and left the tone on the bass wide open, and was happy again. It seemed silly to be compensating by turning down treble with the new pickups when I had just the spot I wanted with everything set flat before. The lows on the MIM pickups are a little tamer (tighter) as well, which I find suits me better through tube heads especially where lows can get really boomy easily.
So, what I have always wondered is, what is supposedly "wrong" with MIM pickups anyway? Why do many of us feel the urge to get rid of those supposedly cheap stock pickups? Do they use cheaper magnets and poorer quality copper wire? Are they wound with less precision or quality? It seems like the components used in making a P bass pickup would be pretty inexpensive to begin with. And the construction and assembly doesn't strike me as rocket science either. I just don't think the MIM, or probably the CIJ pickups are notably worse than the MIA ones. Anyone agree?
Here is the bass I refer to, and it is my favorite (it is very quiet too, no hum, even with what seems like barely enough shielding). It's got some pretty old Fender nickel rounds on it now, and I just really like it: