Table schema:
CREATE TABLE table_26267607_2 (date VARCHAR, circuit VARCHAR, winning_team VARCHAR, pole_position VARCHAR)

Question: On what date is the winning team Abt Sportsline and pole position Mattias Ekström in the Circuit Ricardo Tormo , Valencia?
SQL: SELECT date FROM table_26267607_2 WHERE winning_team = "Abt Sportsline" AND pole_position = "Mattias Ekström" AND circuit = "circuit Ricardo Tormo , Valencia"