I never felt more alive than riding shotgun
In Klein's green 5, until the cops pulled guns
A reference to “Calvin Klein”, not the famous underwear guy, but rather, a famous Brooklyn drug dealer. Klein, funnily enough, later claimed that Jay-Z lies about his past in his raps:
I give him 10% of his life that he talked about; I gotta give him something, [laughs]. He is from Brooklyn, he lived in Marcy Projects, his name is Shawn Carter, he got that right