Thats odd. Ive checked for vac leaks twice in the past month spraying carb cleaner and turned up with nothing. I also took it to a shop that has experience with subies, not tribecas or legacy wagons, mainly sti's/wrx's, and they also applied the carb cleaner spray looking for vac leaks and got no results. They told me everything looks good and thats how a hybrid is supposed to sound and drive... I may have some type of exhaust leak, but i doubt that will hinder performance nor cause fluctuations in the A/F of the car.