MID = Manufacturer Identification
it's a code used on blank discs to signify the maker of the actual media (not just the company it's branded as).
YUDEN000 T02 for 8X DVD+R certified discs from brands like Fuji and TDK which are produced by Taiyo Yuden;
MCC003 for 8X DVD+R certified discs from Verbatim which is produced by Mitsubishi Chemicals.
you can find the MID by using software like DVD Identifier, DVD Infopro and NERO.
EDIT: Prodisc isn't considered very high quality media so that could be the problem. if it's rated at 8X it should burn at 8X. again, the PX716's AutoStrategy feature should help with poor burns, but you need to let it "learn" by burning a couple coasters first.