You could try running a scan on a clean commercial pressed disc to give yourself a reference. I’ve done this with a liteon combo drive. It gives me a rough idea of the burn quality. If that’s a 4x or a 6x burn it’s not as good as I would expect on a 2510. One of the best burns I have ever seen was burned and scanned on a litey 832 (sony 700 firmware) on that media. I have a 2510 that performs very well on that media with maddog 2F7 firmware. My frustrations with scanning on the combo have led me to the BenQ 1620, which has good reading/scanning abilities and looks like a pretty good burner as well.
I’m not sure if anybody knows what the rom drive is reporting or if/how it correlates to burner scans. The rom and combos generally do not respond to the speed control commands properly, which by itself will throw off the results.