just purchased 99 RX300. was slugish on accerlation, changed oil, oil filter, air fliters, idfferential fluids, tranmission fluid. added fuel injection cleaner. that took care of the sluggish acceleration but still has low, 12 MPG average, and high RPM (3000 @ 70 MPH) dealer told me that they replaced the Mass Air Flow Sensor. no check engine light ????