Would there be any chance that a different CD unit would be compatible with the 90-91 Split DIN unit. I have to turn it up all the way, and even then, you can just barely hear it...also, an updated CD player that read CDRW would be perfect...
I don't think changing the CD player will help. The problem you are experiencing is the capacitors are failing in the tape/radio unit. Scroll down this thread to find part of the fix: http://alltrac.net/phpBB2/viewtopic.php?t=190
But, a 1990 unit is a bit trickier, because the description in this thread applies to a 1992-93 unit. See also http://www.alltrac.net/phpBB2/viewtopic.php?t=9466
I'll check the forums you've listed, but the only problem I'm having is with the CD player - AM/FM works great - the speakers are sure showing their age - any bass response is accompanied with buzzing...oh well - I think toyota had it goin on for 1990