A Solution Finally
I finally tracked down what was causing all the buffer problems, is was having the OS, WinXP, on the SATA drive. I tried the big, 250GB, fast SATA on both the MB SATA controller and a Belkin PCI SATA controller. The results were still the same, the "Used Read Buffer" would frequently drop to 20%, 10%, 0%. This would cause the drives 2MB cache buffer to drop to 7% kicking in "Burn Proof" slowing down the burn.
So in an act of desperation, I rebuilt the OS on an old slow 60GB IDE HD that wasn't getting much use. All the buffer problems dissappeared, its rare for the "Used Read Buffer" to drop below 95% now. I can now burn a totally full, 4.4GB, DVD in 6 min + or -, this includes lead-in, track, and lead-out.
-R's consistently burn 5 to 10 sec. faster than +R's, not that it really matters. I burn exact duplicates of each dataset on different brands and flavors, just my level of paranoia.