I realised, felt suddenly that same exultant fever-flash which Faustus himself must have experienced: that of we two doomed and irrevocable, I was the leader, I was the boss, the master. (3.25)
Has Lucius been manipulated, after all? Or is he the one calling the shots? Sure, Dr. Faustus was manipulated by the devil, in a way, but he also chose to sell his soul. It seems that Lucius is entertaining a second possibility here, that it's he who is giving Boon permission to manipulate him.