OK! complete new person here...grandparents bought a Mantua Super Bowl Express set bout 10 or so years ago. No room to put it up, so i took it home for the holidays to set it up. now heres my problem. I have approx 42 cars, one for each team plus some super bowl winners. Have an engine, diesel-electric, guessing your basic mantua engine. I currently have 20 cars attached, 19 reefers plus caboose. At higher speeds, it sounds like the engine is spinning wheels, and i still have something like 20 cars to add on. replaced the stock track with ez-track since it needs to run on carpet, still using the stock power pack. Is my engine just underpowered, or is it something else?