Airflow into and out of an engine is extremely sensitive to changes of this type, and if he still feels compelled to attempt to do this, should do so with the aid of a flow bench to comfirm that indeed there is a significant difference in flow between the larger port vs. the smaller ones to warrant this type of modification. And second to confirm that dividing the port doesn't hurt the flow more than it helps. Never assume that because the port is larger than the rest, that it flows more or better. Also, the larger port would have to be roughly twice the size of the smaller ones to be able to divide it equally to match the smaller ones, instead, by dividing it he will make it much smaller than the other ports. Take this simple example to see: If the large port was an 1-1/2" diameter, and the smaller ones were 1-1/4" diameter. Now divide the 1-1/2" port into two equal divisions....you now have a much smaller cross section by dividing the port. To start with the large port was only about 17% larger than the 1-1/4" port. Now by dividing it you made it 50% smaller than it was, and 40% smaller than the small ports are now! You created far more unbalance now than was there to start with....I say leave it alone.