I'm trying to replace my dead stock radio from my 1990 MPV with a cd player. If anyone has a wiring diagram for the Pioneer radio, model # KE-6501, it would be awfully nice if you could send it to me...

Check with a car stereo place or purchase from Pioneer. You'll have better luck than posting to general forums.

I have diagrams for the unit in the 88 - 89 929, which may be like yours, as I think mine is also Pioneer. However, I've helped others before and in the end, you are probably just as well off to do a few simple checks yourself, as follows:
- Do you have a separate sub-amp/speakers? I know nothing about the MPV, but you should be able to tell if there is a pair of speakers in back connected to a separate amp. The 929's did have this setup, 2 speakers front, 2 in the rear doors, 2 on package shelf (subs). For what its worth, you'll be better off to disconnect the sub amp and use the speakers directly from the new HU.
- Get a small portable radio/boom box or whatever and tap into the speaker leads or headphones out, use these to find all the speaker leads by touching the plugs, key off of course. Make your own diagram for reference. You're looking for 2 front and 2 rears.
- Use an AA battery across the leads found. remove grilles so you can see the speakers. touch battery, cone moves out, the leads are + and - as on battery. Cone moves in, they are reversed. Mark leads for ref.
- All you need now is a test light or multimeter to id a 12V constant wire, an ign switched 12V wire, and the trigger wire from the power antenna, if you have one.
Good luck, and have fun, it's really that easy!