Hey ise300, I had the exact same problem with my 1999 es300. It is most likely your OCV's (Oil control Valves) They get gunked up and don't regulate correctly and it affects your RPM's and Overdrive as well. There is a post on this forum explaining with pictures how to take them out and clean them with de-greaser. Also, take out your MAF (Mass Air Flow sensor) and clean it with some isopropyl alcohol. This regulates the amount of air to gas mixture. If it is dirty the computer will read it incorrectly and give you some problems.
