I have a 56plate 66k, I was having the worst flat spot you can imagine, to the point of being dangerous when pulling out at junctions! Nothing until the turbo kicked in at about 2200rpm. I took it to my Lexus dealer in Coventry, the mechanic came out with me, told me straight away it was the EGR valve, & showed me the readings on his screen, instead of getting 97-98% it was reading 68%! a lost of 1/3 power output!!!
I have had ALL the recalls done before, but he said there was a new ECU reflash 14/06/2010. I had the reflash done free of charge, but had the EGR valve REPLACED not cleaned!!! I picked the car up, drove it out the dealership, & wheel spun off! Couldnt belive it! It was like a new/different car, I gave it some stick all the way home & am still smiling! Was not cheap at £400+ but GOD ITS WORTH EVERY PENNY! The service & help from Lexus Coventry was second to none!