have replaced ecu but still having issues

Lexus Es300, 94, 143k miles. I was having issues with my od light flashing and cel with my car..high rpms and hesitation..dealer said get another ecu..I recently changed out the ecu for a new one. The cel and od light did not come on, but the rpms would rev up moving at 20 mph. it idles lower but still reving at 3000 rpms when i hit 60.What can I do? thanks Larry