Are you saying when you put the car into drive from park? or when you're already in drive, the engine revs but the transmission doesn't catch until you hit the 1,500 rpm mark? If it's slipping, then you're probably due for some fresh toyota oem fluid. if you think you have anything but oem fluid in there, then I would suggest a visit to your dealership for a flush. If you do have oem in there, but it looks brownish on the stick, then I'd do a search for "drain n' fill" to learn the easiest service you can possibly do to the car.
But eitherway, the computer hunts on that car a bit. It's not nearly as bad as others, even far more later models. A very good buddy of mine has an 03 or 04 IS300 in Florida. It's so bad on his, that he nearly got T-boned when he first got it trying to jet out into traffic. He said GO...the car said "WAIT, I'M NOT READY, I'LL GO WHEN I WANT". Last I heard, he was drafting a formal complaint "he's a lawyer" to Lexus and the dealership for ignoring his numerous requests for assistance. That was a few months ago. He still has it though, and says he's learned to understand how to drive it to minimize the effect.
It seems like every toyota product has one goofy flaw that drives people nuts. Just be glad you don't have a GX470, or 4runner, that all have a notorious Clunk in the driveshaft from a sticky slider-sleeve, that makes you think you've been rearended when coming to a stop at the stop light.
It happen when giving it gas after I slow down to almost a complete stop for turning rigth or left. the transmission doesn't catch until rpm hit the around 1,500 rpm.... that is why I feel more tranmission issue than throttle lag. I just did Fluid Flush (drain and fill 3 time with T-IV) but sitll same...
Is this Normal or has issue???
Thanks!
I have a similar issue on my 2000 ls400. It's seems to slip more often after i make a turn. I've flushed the tranny oil with IV fluid and it seems to be somewhat better. On my '94 ls, the accerelation was much more linear and there was no lag whatsoever. The breaking was also much more intuititive on the '94 ls than my current '00.