A "Power Calibration Error" message has nothing to do with compus power supply (PSU).
This error is media related. When a drive first starts to write to a disk it will burn a small amount of data to a calibration area on the disc, using the calibration information in the Media ID code, and then try to read back the data that it has written. If it cannot be read, then disk will be rejected and fail with a power calibration error.
sodeysay, first check at what speeds those TYG02's are supported by your I/O Magic (use CD-DVD Speed -DiscInfo). Try to run a Transfer Rate Test with CD-DVD Speed on your "98%" disc.
Some kind of burn log would also be of interest.
BTW, can somebody explain this quote if DMA is on;
Also it takes very long to scan and does not go over 0.69x in Nero CD Speed Quality scan..