They are claimed to be Pakistani, But maybe they are Chinese and being branded as Pakistani.
Yes IK20 are iridium plugs, Not sure about mileage but the waste spart system (2 coils 2 plug wires) systems are suppose to work better with iridium plugs.
Some people might tell you that you should use ik16 but on Densos website IK20 is recomended because of the waste spark system.
Waste spark system applies to Santro, Baleno, Liana, Jimny, APV, Lancer