"Ionized flak" is when you take a capital ship and combine Cluster Flak Arrays with Ion Disruptors in the same gun battery. The Ion-Ds can use the shrapnel from the CFAs to jump between targets, greatly increasing the weapon's range. Ionized flak is prone to friendly fire.
"Pirate Alley", also called the "Pirate Highway", is a cluster of pirate sectors in the northwest region of the universe map in X3.Specifically Farnham's Legend, Bala Gi's Joy, Olmancketslat's Treaty, Split Fire, Brennan's Triumph, Danna's Chance, Nopileos' Memorial, and Hatikvah's Faith Fleets clash there all the time, and scooping up random drops is a good source of income in the early game.
Manual Misprint: X3: Reunion's manual was wrong in almost every way. X3: Terran Conflict's manual is more accurate, but some images are wrong (Boron ships with an Argon ship for the picture) and it talks about weapons that don't normally exist in the game.
The Bonus Pack scripts released for each iteration of the games are the best-known, officially signed mods that won't mark your save as "modified". Also the X-Superbox also includes three fan-made soundtracks, additional signed scripts, and PDF versions of fan fiction from the forums.
The 3.0 patch for Albion Prelude is composed almost entirely of content written by the AP Community Project, a group of X modders brought in by Egosoft to get more content to tide over the playerbase while X Rebirth battles its way out of Development Hell.
The developers of the X3 Xtended mod, who were later hired on by Egosoft for Terran Conflict. In turn, some of the guys who worked on Xtended Terran Conflict were brought in for Albion Prelude.
About half of the new ship content in Terran Conflict (Heavy M6 ships, a full ATF ship roster, frigates) originally appeared in Xtended, albeit less polished-up. Likewise, much of the new content in Albion Prelude came from Xtended Terran Conflict; the M7C Drone Frigates, Yachts, and Heavy Freighters (TS+) first appeared in the mod. The Stock Exchange is based on a script for X3: Terran Conflict, but is more fully integrated into the game and easier to use.