Nephi is on Major Dhatri's hit list for the quest Three-Card Bounty. Dhatri states that 1st Recon had previously been sent to kill Nephi, but proved unsuccessful after multiple attempts, as Nephi tends to use his own men as meat-shields to protect himself, and is also tough enough to have managed to survive despite 1st Recon snipers having managed to land at least a couple confirmed shots on him.
Major Dhatri also warns that Nephi is exceptionally fast, having earned his nickname by managing to kill a dozen armed NCR troopers in melee combat before they even knew what hit them. In fact, he moves 25% faster than a normal human non-player character.
Bert Gunnarsson will comment on Driver Nephi's passing after his death, but will not elaborate further on any prior relationship he had to Nephi or the Followers of the Apocalypse.
Driver Nephi has an unused unique dialogue tree in the GECK, in which the player can ask him basic questions about himself, his golf club, Violet, and Cook-Cook. This dialogue also reveals that Nephi is from Utah, and was once a friend of Bert Gunnarsson and a member of the Mormon Church before he fell under the influence of the Fiends and became Driver Nephi.
Driver Nephi's name may be a reference to Nephi (pronounced /ˈniːfaɪ/) which is the name of four prominent individuals in the Book of Mormon, the religious text read by the Mormons, and also the name of a city in Juab County, Utah. This may further suggest Driver Nephi's affiliation with the Mormons at New Canaan (mentioned in the cut dialogue found in the GECK).