thinking they apply because they are called "Express lanes" in Utah? The original purpose of HOV lanes was to encourage carpooling during rush hour not to provide an extra lane for speeding.

Left lane = Speeding
HOV / Express lane = Carpooling

If you want to speed in the carpooling lane then fine but don't get all grumpy when other people are using it for a different purpose than you are. If you are so concerned with speeding then stick to the left lane.