TIE/x2 starfighter

The TIE Advanced x2 (TIE/x2) was a TIE series starfighter prototype created by Sienar Fleet Systems. It incorporated many of the design innovations from the TIE Advanced x1, including higher performance ion engines than the TIE/ln starfighter, a hyperdrive, and improved combat software; it also possessed a hull that was a departure from the TIE series standard, and inward-swept solar/radiator panels configured for higher pilot visibility.

Thirty-two TIE/x2 starfighters went through field trials for nine months under some of the best active duty TIE wing commanders in the Imperial Navy, where they were carefully monitored by teams of diagnostic droids, maintenance techs, and engineers; their reports (along with glowing reports from the pilots themselves) gave the SFS TIE Mod Team a solid profile of the ships' perks and flaws. The ships were returned to Lianna at the close of the trials.

Behind the scenes
This is likely the same ship type as, or a predecessor of, the TIE Advanced ships seen in the Star Wars: X-wing game, despite Imperial Defense Daily's report claiming that the ship was not to see active duty service. It is probably also the TIE Advanced model mentioned in The Far Orbit Project.