Well, I got a gallery where I sometimes explain how I did it.
-I resized the picture to 600*450.
-I messed around with "image-->adjustments-->levels".
-I messed around with "image-->adjustments-->contrast/brightness".
Note: I dont only adjust the whole picture, I often make new layers via copy, and erase the background for example to seperatly adjust the levels and contrast on the car. And vice versa. See my tutorial on the layer stuff.
-I used a technique of motion blur (if you go to my tutorial in my sig, you will see a link
in my tutorial again, for how this blurring technique works).
-Then I copied a layer, erased the car and went to "image-->adjustments-->hue/saturation". Now for the first picture I increased the saturation with...I cant remember, something like +30, I don't know.
For the second picture I decreased saturation with something like -50.
-Then I went "filter-->sharpen" and just used the first sharpen option.
-Then I got the blur brush, set the brush size to 2 pixels and zoomed in on the edges of the car. I blurred the parts that were pixelated/
too sharp.
-Then I added a little border and saved it as JPEG with highest quality
Really, you should start a gallery in the video/photomode section of the GT4 forums. Thats where I learned all this stuff.