Its already been said, but I would like to re-emphasize the fact that some boards are just SLOW.
I was on a trip to Vail with some friends-of-friends. Vail is huge and has a ton of terrain that is not-quite-a-catwalk and not-quite-a-slope. Anways, this guy would routinely lose speed a couple of yards before the rest of us. He and his brother were similarly sized and similarly skilled, so I am not inclined to think it was a technique issue.
I tuned the guy's board for him that evening at the house with the same wax on my board, but it did not make a noticeable difference. He even went so far to have it waxed and tuned again (this time by a shop). I can't say for sure if the 2nd tuning did him any good because I didn't spend that much time riding with him after.
Anyways... try switching boards with one of the other guys to see if that makes much of a difference.