Yes I remember you, car is not with me now a days. I will update you very soon regarding cylinder size.
For plugs, I installed plugs and then went to Pak-Suzuki for routine tuning. I am not happy with Pak-Suzuki this time. Car is not giving me driving charm and I have no time to return back to them. Car is dropping RPM to 500-700 when it is idle and start vibrating. Sometimes engine shuts down when brakes are applied and speed is reduced to zero. On CNG its running perfect. However, I observed change in pick and smoothness of drive. I think spark is strong enough on CNG as plugs are installed with default gapping.
Next plan is to upgrade plug wires and ignition wire to balance current to plugs. Saving money to purchase good quality cables 