The pinion gear sounds a little high for most situations. Just from the info you have given, I would suggest dropping to a 25 or 26 tooth pinion if it's 48dp.
+1 on asking what your current car/gear ratio is, and where you race (or do you just bash?)
Info like that should help give a better answer
In any case, it sounds like your motor might need a skim (if you're not sure of the process, ask an experienced racer at the track and they can fill you in with how it's done) and possibly some new brushes too if it's been overheating, as they will change colour and loose their performance, slowing the motor down...