Sorry. I was so busy that I didn't visit the forum for a long time. Just want to post some of my experience about my cold start problem.
-- My Problems: In cold start, the engine was so noisy. The car jerk when shifting from R to D.
-- What I Have Done but didn't help: Flushed the engine with Karosen; tried different brand of engine oil; used Toyota oil filter; used Seaform through throttle body, gas tank and engine oil; install new dog mount.
-- My Lexus dealer said: There was nothing wrong after one hour checking and give an check engine light on (more about this later)
-- My Experience: One day, I pick up a K&N filter to see how good it is. The problem almost gone: Less noisy in cold start. No more jerking when shift from R to D. I am not sure the new filter help me but after one NY winter, the problems didn't come back.
-- Some more experience with a Lexus deler in NY state: When they gave me back my car, the check engine light turned on when I was on the way home. When I came back, they told me that they can reset to turn off the light but my Cartalic converter was gone so the light would come back very soon. They gave me a quote for about $3,000 to get it fixed. One year later, my car still running without any check engine light!!!
Hope my experience can help some one.