Personally I think there is no use of putting other than standard plugs in a Mehran. A carb., 800 cc eng. (early 80's technology). It just cannot digest these 2 or 4 tip, this or that sort of plugs....
You might get a little more boost if along the plugs you change the coil, plug wires etc. What I think a simple Bosch plug is good enough.
Currently in my Mehroo I am using original Bosch plugs and done like 40k km and still in perfect shape. (I know one is suppose to change long ago but they are just perfect so what is the use).