All those scans are excellent
with the exception of the one with the PIF of 9 at the start, and the scan with the periodic high PIF's.
The high PIFs can be caused by several things.
1) Nvidia IDE drivers (try using MS standard IDE drivers)
2) Incompatible devices on the IDE chain or faulty IDE cable. (Try moving the burner/scanning drive to a different IDE chain & cable.)
3) Power supply issue (replacement required)
4) Faulty drive (replacement required)
Unfortunately, I had a drive (sohw-812s) with similar scans, on various DVD-R media. The drive broke down shortly after scans like that appeared & refused to burn / read any media.