Let him run in for a half hour in each direction just in case it is a breaking in thing. I believe all the locos you mentioned have the same motor, so they should be running at the same speed. I know that's the case for my copies of these models.
If it doesn't improve after complete breaking in, you can contact Bachmann directly and they'll help you get it repaired or replaced. Hope this helps.
If it doesn't improve after complete breaking in, you can contact Bachmann directly and they'll help you get it repaired or replaced. Hope this helps.