ik20 is for performance ,vk20 is for people who need to go for long drives on a frequent basis,vk20 is expensive n isnt avaliable in pak,that leaves u with ik20 
ngk laser iridiums or ngk bkr6eix11,better to go for bkr6eix11 or denso ik20 or ngk bkr6egp,the iridiums are usually for honda k series engines,the plug code reuired by u isnt avabliable in Pakistan
Ur engine should peform better as comapred to before when the car was in copper plugs