Two wires which comes from Advancer Emulator are for MAF sensor: MAF sensor is primarily responsible for changing the timings. Its measures the data, sends information to ECU and ECU calculates new timings for injectors and ignition coils. Now in CNG, one wire from advancer cuts the MAF sensor signal wire and is routed via return wire from Advancer Emulator to same MAF sensor wire. Once CNG switched is turned on, advancer is on, measurement from MAF sensor are manipulated and sent to the ECU as per CNG algorithm and in return calculates new timings which works well with CNG kit.
Two wires from advancers are connected with TPS sensor and remaining two sets of wires for oxygen sensor are connected only if oxygen sensor is present on this vehicle. If you have OBD kit and you measure the STFT on CNG then you will realize that this value will start to decrease as soon as CNG is turned on and as soon as it hits -25 % then your engine check light will be on. STFT is short term fuel trim, values calculated by ECU because of reading from oxygen sensor and reading is air to fuel mixture ratio for engine. Advance/emulator once connected will fool the ECU regarding content of oxygen in exhaust and thus will avoid unnecessary engine check light on CNG.
Advancing timings via distribute is not needed, Advancer/emulator will maintain CNG timings on CNG and Petrol timings on Petrol.