1. Tune & make car mechanically good. Be a economical driver
2. Carb cleaning, Plug clean/replace, Air Filter/Fuel Filter replacing. Engine oil condition
3. I know only EFI tune-up places in these area. Don't know they carry out carb..
4. Depends on the model. But for most in Idle, 700, With AC 800, In gear 600
5. Ya it's a factor(not a Big) . Back pressure is a performance factor.
6. Not fuel saver liquid but fuel system cleaners. Most are used by EFI system to clean even injectors but you may use "wu**h"
7. maximum consumption is 0 Km/L [A owner will help you on this]
8. A place @ Malabe-Athurugiriya road befor Arangala juction I think. Check to see...