The drive does not like to read burned disks at 16x unless they are PERFECT burns, mine does the same thing. Some of the drive apearently do OK but most are like ours when pushed. Try going down to 12 or 14x max with the hack and see if it does better.
If my 166 does read all the way to 16 smoothly it is truly great burn, some of mine will do it. I might drop down a peg in rip speed too but it is very good for picking out the best burned disks I have made. Doesn't seem as picky on stamped movie disks by the way.