Got a 2004 3.9L V-6 w/ automatic. My friends tell me to manually shift gears when I race from a stop. They say to put it on 1 and go to 2 when rpm is near redline and go to D when it gets near redline again. They say it'll go faster. Is this true and how much faster? If true I've found through experimenting that it feels smoother depending on when I upshift, when should I aim to upshift for best results?