The midfielder was bought by Martin Jol in the summer of 2007 but was a rare starter under Ramos, making just seven starts in the Premier League last season.
Boateng moved to White Hart Lane from Hertha Berlin and is now poised to return to the Bundesliga, with the 21-year-old expected to complete a season-long loan move with a view to permanent switch.
Speaking in the German media about Boateng's future, the player's agent Jorg Neubauer said: "Kevin has decided on Stuttgart, now the two clubs have to agree."
Meanwhile, Stuttgart's general manager Horst Heldt admitted: "Boateng is a very interesting player. We are in talks."