Hi ccanupii,
In the enginespec config you can change the maxspeed, max-accel and max-decel values to give a different performance to a loco. But be carefull and make a copy of the original first in case it does not come out as you want it. In TRS2006 this can be done in CMP, in TRS2004 it can be done in TrainzObjectz if it is not a built in item.
Cheers,
Bill69