In the beginning i would suggest you stay stock. Retain the oem filter box of the cultus (efi version of course), stock plugs and stock plig wires, stock headers and stock exhaust system.
Try to get everything working properly first and remove any possible errors causing the annoying check engine light.
I was getting about 15 to 17 kmpl in my car from that motor. However i was not running any extra weight in the car, no aircon, no sound systen, no spear wheel, etc.
Didn't install cng so no clue on mileage on that.
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