What is the color of the smoke, white or black? White smoke indicates burning of oil means rings are weak. Black smoke indicates that extra fuel is being injected into the engine which also smells strong like un-burnt petrol & it irritates the eyes.
Check if your MAP sensor pipes are connected to the engine. That also causes black smoke to appear from the exhaust. (My car had the same issue) Also is your engine producing noise (knocking) when you accelerate your car? If yes then the timings are not proper & they need to be adjusted.
Althought my car petrol avg is also not so good, maybe 8 or 10km/ltr. I think an avg daewoo gives mileage around this figure.
I am not an expert but learning with each time I get a new fault with my car. The experts here will guide you even better.