What I have found is that with my races I tend to run faster than what I was training at. The more mileage I put in the better my endurance so I am able to push myself longer at a faster pace for a longer distance.
For the 10K that I ran last Saturday I had been training around a 7:40 pace yet I was around a 7:20 pace for the race. I attribute this to the fact that I am now competing with others so I like to pass or hold steady rather than being passed (I drive this way too so it could just be me) and the adrenaline factor comes into play.
You could also test the pickle theory at another race...you could be on to something.