Just remember that after you have it flashed you can't go back to the previous ECU program! The people that have complained about the slowing down and then trying to accelerate smoothly have found that the flash didn't help that problem at all! I've found that after the final flash on my '03 ES: The car lost the quietness when accelerating normally, since the RPM's to upshift were much higher as indicated on the tachometer, and the only way you could force the transmission to upshift was to slightly take your foot off the accelerator pedal. I also found that, my gas mileage was lower.....whether using Regular or Premium fuel. On top of this I found out from reliable sources that the car no longer would meet ULEV specifications, and the reason that Lexus developed the final flash was to try to satisfy their customers, rather then to address this problem correctly. I believe this, since the ES350 6 speed automatic exhibited none of the problems of the former generation ES's. I was so frustrated after suffering for 3 years of ownership of my '03 because of this problem, that I traded it in....with only 16K miles.
P.S. Here's the first post that I made about this problem in May,2003.......sound familiar? >http://us.lexusownersclub.com/forums/index...c=3584&st=0