Formula for AP-Applied MP

That's not really a formula at all O__o. Because you definitely get more than 14-16 MP if you spend AP into MP while wearing INT gear on.

There's no formula for how much you gain when you put an AP into HP/MP. It's simply a set number affected by how much INT you have

But I was answering your question:
"What is the exact INT amount required for a pirate to wear so that it will gain enough MP to AP reset TWICE out of MP?"

In which the answer would be 340 INT.