Do remember always do clean your air filter after 2500 KM (Just pay Rs. 20 or less for blower cleaning) and in dusty areas (like now a days in RWD/Islamabad due to construction) after 1800 KM your milage will quite maintain and must change air filter after 5000 KM or when necessary,
Also use soft pedal so that gear shifts quicker at low RPM
Do not only tuning but also CNG kit (if possible of cylinder) turning as well
Remember Use the petrol or CNG from trusted pumps that is also alot matters
Maintain Tyre Air pressure