see , installing a ngk plug and telling performance increase is just like u wearing brand new shoes and telling u can run faster... its all how much energy is being created..maybe ngk's are producing better and effective sparks... u may go for it to give it a try
put good fuel.. maintain a good clean air filter and fuel filter... ur co % should be in check.. even while doing an emission test it will show co %... my co % is 0.2 %
its not compulsory to check it in pbk... but ask them to adjust it a bit..