Hi Monsterped. What sort of miles you are now getting. Mine has just come back from Swindon Lexus had exactly the same trouble as you. It registered 42mpg when it came back, got worried as when we drove it yesterday it dropped to about 35 now managed to get it back up to 39mpg.
How did you get the extended warranty as mine is up in November, these problems been ongoing since we bought the car in May.