I am 45 years old over weight by 10 pounds. I ride a Trek Madone with a regular helmet, other than that, how can I go 1 mph faster?

Any tips? Any position tips? How much faster will aedro bars help? My last tri-sprint was only 18.1 m.p.h. I need 19 plus. How much faster is a tri bike in mph? Will new tires go faster than stock tires? What kind?