There are really only two factors that will affect your speed on the flats: rolling resistance and aero drag. You could change your tires (23mm) to lower the rolling resistance and then work on aero drag. At the moment you probably have a fairly upright riding position. For a quick experiment you could try lowering your bars by flipping the stem and removing any spacers under the stem. Try a couple of laps with your arms bent and your head lower and you should see an improvement but it's unlikely to be 3mph.

Expensive components will make your bike lighter but won't, by themselves, give you any extra speed.