A few of tips:
I don't think the 2003 supported reading MP3 disks so you are likely audio CD only.
Don't use the stick on labels. They can get warm and come off or gum up the works on your headunit.
Not sure what burning program you are using. If you are on Windows I've been using these lately:
cdrtfe Portable (cd, dvd, vcd burner) | PortableApps.com
InfraRecorder Portable (CD/DVD/ISO burner) | PortableApps.com
Though I generally have better luck with my Linux laptop (newest hardware I have with a CD drive so may be related to my windows drives being older.)
Have your burning program limit the burn speed to 1x and see if you get more reliable playback. If you get a few good burns at 1x try 2 or 4x and see if the results remain. Stay below the stated recording speed of the discs, Especially if they are older stock.
Enable buffer underrun protection in your burning program. Also when running the burn have the source data on your local harddrive (not NAS or other remote storage) and don't do anything else on the computer while the burn is running.
If you are using the "white label"/generic bulk spindles of blanks (the ones office stores, Best buy, etc used to giveaway "free with coupon" to get you in the door back when your 4Runner was new.) Try Verbatim CD-R (NOT CD-RW). If it's a mix you'll keep for a while the ones that look like old 45 single records have worked well for me.
Best Of luck getting clean burns.
Boort