I have a 2510A, and have been using TY 8x discs for a while now. I bought some Ridata 8x media, and they burn with shrink/nero @ 4x. Is that due to the firmware version I'm using?
Yes it's in the firmware. Upgrade to a newer firmware or an unofficial one.
If this is Ritek +R R03 media, some NEC firmware, and others as well, limited the burn speed to 4X because of quality control problems. Possibly that is the case here.