Honda city IDSI 2005 model milage issue

[qazishoaib334]

Assalamo Alaikum. I am using honda city ids 2005 model since 2019. Before changing spark plugs from denso iridium to NGK iridium it gave 17+ km/kilo in local and 25+/kilo on long route on CNG but now when spark plugs changes to NGK iridium its local milage drop to 12 hardly on cng. What is the possible reason. I already done tunning but still same issue. Thanks for your suggestion in advance

[hash4u]

new plugs?
as per one of my friends who runs a workshop market is flooded with fake plugs
try to arrange kabli plugs in condition and recheck