I know this is a old post but, Did you replace both sensors? I had a 96 es300 I had to get both sensors replaced and the wiring harnis! Also I had a problem with my 2000 es it wouldnt change gears right, and it wouldnt go over 80, kept studering. For me all it was was a dirty mass air sensor. I took it to lexus of Norwich and they just pulled it off and cleaned it with a rag been runing great for almost 2 years!