NPI head porting w/PI intake

You're not leaving a huge amount on the table.....3-4hp with a N/A engine at the most. The advantage of the PI heads isn't necessarily the larger intake ports alone, but the combination of the larger ports, revised combustion chamber and PI specific intake and exhaust valves, that when used in conjunction with one and other provide better low speed mixture and less shrouding around the intake valve. Guys going with nothing put PI cams and intake on their Non-PI engines are coming within 5-10hp of the '99-'04 PI engines

You could clean up the edges if you wish.....there's lots of material there to work with, but like I said, it's not manditory for good performance.