I have two Bachmann DCC locos: 1 purchased w/ DCC and the other I upgraded to DCC.  They are both SD40-2s.  Is it common for the 2 locomotives to run at two different speeds even though the controller is indicating they are both running at the same speed?  I have them both set up for 128 speed steps.  I am using a MRC  Prodigy Express DCC controller.  One loco can be set to 50 (native DCC loco) and the other (upgraded DCC loco) to 50 and the native DCC loco will catch up to the upgraded engine in about 10 laps around the track.  Any suggestions?

Also, where can I find a list of all the Bachmann supported DCC CV#s and what each one of them do?

Thanks