Aren't the shots posted the second time a lot clearer simply because they have been resized? One of the reasons I rarely post shots above 800px resolution.
My experience on motion shots:
1) If you're rig mounting, stability is critical. Drive (or better still, push) slowly on a smooth surface with a long exposure (in seconds that is)
2) If you're shooting car to car put your camera on rapid fire on a slowish speed (fraction of a second) and find the 1 sharp shot from the 100 you took.
Great work, and always remember all the pros you mentioned earlier started out the same way - experimenting and testing. Get used to the feedback (positive or negative) - people love to give it! Not to mention advice, you didn't ask for.