Sir you can remove the CNG.
Else, Tune the CNG kit, service it, remove oil, adjust CNG flow, maintain air flow to air intake, service/replace spark plugs, do the same with power wires, check battery/grounds wires and terminals, replace if in bad condition, check the carburettor, wash and clean, adjust the jets, set the valve clearance, check the headers/exhaust system (Dholki) for clogging, replace if necessary, check air and fuel filters, engine and gear oil, clean or replace if necessary, check the fuel lines pump for petrol performance, also the clutch play, accelerator wire and make sure the petrol tank is not rusty, also check the radiator and fan for proper engine cooling, engine gaskit, tappet and rings seals, engine oil and mounts for power and smoothness. clean and adjust Distributor and ignition for proper timing fuel efficiency and power.
Also clean parking brakes and front rear/discs and drums for proper braking.
Also get the alignment done.
Regards