you can maintain it all you want - the inherent nature of the GDI engine is that it generates a lot of soot because of its high compression ratio and that its an extreme lean burn engine. This along with a giant EGR system causes the piston tops to carbonise and piston crown crescent loses its shape, which is vital for creating that little tornado storm in the cylinder in which the fuel is injected and the engine fires.
All this is aggravated if you drive it slowly all the time. It requires a scheduled maintenance of blasting out the carbon from the cylinders, like I said where these cars were OFFICIALLY sold - they ran ok as the dealerships had the machines to clean them out. the Pakistani mistu dealers dont have it and dont offer any support for it. They cannot even clean out the injectors as they run at 2000 psi pressure, your regular EFI injector pressure is 45 psi max.
Some owners faced heavy repair bills including replacing the high pressure fuel pump for no reason (hawaee tukka of ustaad) or the AFM (another tukka)
The cars dewan sold were a 2.0 litre carburettor model, a 2.5 itre V6 (which was probably the oldest model of V6 mitsu made) - it was 2 valve/cyl. engine. They looked OK but actually were as technologically advanced (engine wise) as the 80s. - which made them perfect candidates for CNG swaps.
The swaps I did made them the car you would never let go. Smooth sound, good fuel economy, good power and all luxuries with nice looks too.