^wrong. it ensures the proper burning of CNG by letting the right amount in into the engine. it gets in input from the exhaust end. yes the O2 (i mean the mass air flow sensors at air intake side) sensors can tell how much air is coming in and basd on that fuel can be injected to keep the air-fuel mixture right. but then the exhaust sensor (or CO2) forms another control loop that also helps to control the fuel injection. in cng kits i dont think O2 sensor gives any useful input so thats why lambda system is required or maybe it does an it tells the emulator the amount of fuel (petrol) to be emulated and CNG to be injected. but the lambda control further corrects the CNG amount to be released.
are lambda sensor and the sensor at the exhaust end the same??