FYI, Some drives, even though they support overburning, will overburn better than others.
I have a Sony DVD re-writer and a brand new Lite-on DVD re-writer. The Sony one will burn right up to 900+mb per disk, but it seems the Lite-on will only burn up to 800Mb. So the Lite-on is being returned...
The lexus stereo will only read up to 878Mb on a disk.
Also, if you do "disk info" in Nero, ignore what it says about the capacity of the disk. If the CD-R is a 900Mb one, it may still show 703Mb. Mine do, but work up to 900Mb.