i think we are missing the fact that tires are a measured in certain size. you can increase width and keep the same height. you just wont keep the same aspect ratio for the tire. a 275/4017 tire is about the same height as a 245/45/17 tire, even though they have different aspect ratios (the second number in the size).
for the stock 16" V6 wheels, they are 7" wide. about the widest tire that should be used on a 7" rim would be a 225 or 235 width tire. find an aspect ratio that makes the tire close to the stock height if you dont want to change anything with a tuner. a 235/60/16 tire would be about 27", or the same as the stock 17" wheels for the pony package cars. i dont know if the 16" tires are the same height as the 17's. what size comes stock on the V6 rims? then i can run the specs and compare them.