Earlier today, Rockstar Games issued an advisory to Xbox 360 owners that warned them not to install the Grand Theft Auto V Play Disc as it could adversely affect in-game performance. The advisory came via the company's Twitter page and said, "For optimal performance, we recommend not installing that disc. We will have more info on our support site at launch."
For those not familiar with what a "play" disc is, GTA V for the Xbox 360 comes on two 8GB discs, with the first being an "install" disc and the second being a "play" disc. The install disk is mandatory, while the play disc can be used to play the game or install the full game on the console. No information has been given on if or when this issue will be fixed, so for now do not install the "play" disc and just run the game from the disc instead.