Remove the tip, take it to a tool specialist eg Specialty Fasteners. Ask them to sell you a drill bit the same size as the existing holes.
Drill the extra 2 holes into your tip.
Test the outcome on your machine.
If the steam dies in a very short time and doesnt recover then the volume of steam your "new" tip is flowing is more than the capacity of the machine to recover.
In that case fill the extra holes with solder taking the tip back to its original design.
Personally, I wouldnt do this. I dont think the machine has the capacity for you to double the steam flow from the tip but, youll never know if you dont try and.....I could be wrong.
You cant compare the steam capacity of your Minore to any full size commercial machine of any brand, model or type - the steam tip needs to be properly matched to the capacity of your machine.
Its likely the only way you might be able to go from 2 to 4 holes in your tip and not lose capacity to recover is if for example, you halve the size of the holes therefore still only flowing the same amount of steam from the 4, as from the original 2. If the result from this change to the tip works better than the original, it would be due to the different configuration of flow, but........it might not work any better than the original. *
Goodluck in your R & D.