Anytime I’ve got a window or sunroof open over around 50mph I get really strong exhaust fumes in the car. Just wondering if anyone has had the same and found the cause? Over the years I’ve had two 5door cars and two 3door and both 3door cars have had this problem but not the 5door ones. Car in question has a new Miltek system with no leaks. Body and floor are solid, no holes. Fitted a new boot seal and checked the ventilation flaps at the rear, near the bumper. Even removed flaps and taped up the aperture, no difference. Any thoughts greatly received. Ta!