Solo upgraded the Millennium Falcon's engines to a Class 0.5 hyperdrive, giving him twice the speed of the Empire's ships. With a stripped-down design, the Millenium can engage hyperdrive in as little as three minutes, thanks also to a Quadex power core, also not standard on a YT-1300.
The Falcon was outfitted with "duralloy plating" to protect the hull, and armor plating on the docking arm at the starboard side. Solo stole shield technology from shipyards to give the Millennium Falcon battle-grade protection. The Kuat Drive Yards, Novaldex and Nordoxicon let the ship hold strong against weapons that would decimate a normal YT-1300.
Advanced sensor suites are incorporated into the Millennium Falcon's back sensor dish, giving the ship a detailed view of its immediate and long-range surroundings. Solo also added sensor jammers to hide the ship during battle.
Prior to Solo taking ownership, Calrissian replaced the YT-1300's standard mandible mounted blasters with Corellian Engineering Corporation AG-2G quad laser cannons. Solo enhanced the Millennium Falcon's armament further when he added additional powercyclers, high-volume gas feeds and laser actuators.