You are using Kprobe correctly, except for the scan speed. Please redo your Kprobe scans at 4X scan speed, the forum standard for comparison. You can read Interpreting PI/PO error scans to find out what these graphs mean. PI/PO is now referred to as PI/PIF. Roughly, PImax<280; PIFmax<4. That means your disc probably will have trouble being read if it shows many PIFs over 4 when scanned at 4x scan speed. A disc can be bad and have no ‘errors’ recorded under that heading.
Princo media is known as very poor quality media :Z . I think that is the source of your problem. Try a forum search for Princo and you will get tons of bad reports. Try some better media. You can read around here to find what media is available in your area that will give you good results. My personal favorite is Fujifilm-branded 8x+R Made-In-Japan YUDEN000T02. They are also available under several other brand names.
You can also flash your drive with special SOHW-832S firmware, which may give you better results and expand the drives capabilities, but will void your warranty(which is probably gone anyway by now). Many around here, including myself, have done the cross-flash with great results, thanks to the C0deGuys