You dont need a good mechanic unless you have tried following things...
1. Use 05w30 engine oil. Shell helix ultra, havoiline formula or Toyota genuine motor oil that comes in a tin pack.
2. Clean or replace air filter
3. Get your throttle body cleaned asap as it gets some black carbon stuff deposited on it
4. Get your spark plugs cleaned
Try the above things as a good mechanic will also perform these things before going any further.
Here are few things if the performance does not improve.
- Catalytic converter needs cleaning. Never remove it otherwise it will give a terrible sound.
- If the fuel filter is blocked, it gives the same problem as yocurs
- Check the cvt oil. Colour and smell of the oil tells you if you need to change it.
I am from Lahore so no idea about a good mechanic. Just visit nearest auto market and see the workshops yourself if they are repairing vitz and also check if they have a scanner to check computerized cars.