Slower in DCC then in DC

[Charlie B]

Does it run great in dc, and are you refering to before you added DCC? Adding DCC can help with a little better control and fine tuning, but it will do nothing to improve a mechanical problem. If the drive train is free and it runs good on dc it should run fine on DCC. You might check the back emf settings and the kick start settings as well.
This gal should be able to creep around a level layout with 5 cars IMHO, and the NCE decoders are among the best.

Charlie