when engine is under heavy load at low rpms (1000-3000) it makes a funny rumbling sort of noise. this is made worst if the AC is on or the outside temprature is hot. i use scangauge 2 to monitor engine load mpg etc and i noticed this noise comes up when engine load hits 99% (max load). this doesnt happen under full throttle. anyone experienced this with the 2.5L?