Baleno came with Carb before 2002
Baleno came with EFI from 2002
To resolve the issue of back firing is to change 2 plug waste spark technology (original - G13B) to 4 plug technology (baleno 1.5 imported engines G15A).
Apply thin layer of dielectric grease to coil's boots at plug end.
Baleno with FF CNG (if injection technology) perform better, same as in Liana.