with wider tire, you actually want to decrease your tire pressure to keep load ratings the same. of course most folks actually increase with larger tires.

the best thing you can do is to inflate to factory pressure (should say what it is on the inside of the drivers door jamb. i know the 00 and 01s with 18 inch wheels specify 29psi. i dont know if the 99s are the same with the 16 inch wheels

once you are at factory pressure, take a grease pen or piece of chalk and draw lines across the tread on all 4 tires. drive straight 50 feet or so and check to see how the lines have worn off. if the line wore in the centers of the tread, you have too much pressure. if the line wore more towards the edges, you dont have enough pressure. if it wears on only one side or the other, you likely have an alignment issue to address

there is probably a 5-7 psi range where the wear will be even, at that point it is personal preference, more pressure will increase ride stiffness and steering response. less pressure will give a more comfortable ride

whatever you do, do not exceed the pressure printed on the side of the tire. some folks will tell you to inflate the tires to the pressure printed on the tire. this is a mistake and will almost without a doubt result in uneven wear