I did a little above average on the MCAT (if I remember correctly...it was a million years ago!) and I did a little above average on the USMLE step 1 (which wasn't THAT long ago). Course I may have just been at a "little bit above average" point in my life because on Step 2 and Step 3 I was at a "shining star" stage in my life (recently married, totally enthusiastic about everything) and I did excellent on both of these exams. I would not worry too much, correlations are not hard and fast and rules...