Style chooser

Hi to all, i recently own a 97 Satria 1.6 with original Mitsubishi ECU. I have read alot about how 1.6 engine will be more efficient in fuel consumption than 1.3 because of the power to weight ratio. Note that my satria are in original condition including the exhaust except the exhaust header which the previous owner change it to 4-2-1 type. What has raised my concern is that my brother own a 2002 Satria 1.3 VDO with exhaust mods. We did a little test where he drove both car in a week time...