My LC80 (not converted) 4.2L Tdi, A/T, currently emits a weird sound. When you accelarate it abruptly, out comes a 'whistling like sound'. This occurs even in low speeds as long as you accelarate it abruptly. If you drive normally, the sound does not come out even at high speeds. The sound does not affect the performance, or so I think, but its really bothering. This wasn't there before. Any advice? Thanks in advance.