My 94 LS400 hesitates, almost shuts down and the engine light comes on when trying to accelarate over 2000 rpm's. The Toyota dealership first said the car was throwing codes for the Throttle Positioning Sensor, they replaced, car worked fine for one day then problem came back but the TPS codes went away. Then the codes for the IAC valve and the Mass Air Flow came up so Toyota relaced them, car worked for one day them problem came back but both codes went away. Finally Toyota said the ECM (car's computer) needed to be replaced because it was throwing wrong codes. I could not afford the Lexus ECM ($1,400) so I had Toyota remove the ECM, sent it to Auto & Truck Electronics (they specialize in rebuilding these ECM's), they rebuilt it, Toyota put it back in and again did fine for one day and started the problem again. I am begging for an answer here! Someone please help...