To be honest, most radios ARE undertuned. You CAN get set up to run at
the full legal 4 watts, and not exceed modulation limits. Just go to a
trustworthy shop.

This shouldn't surprise anyone.

The manufacturer has to certify that none of the radios built will exceed
legal limits, so they are all designed to fall safely inside. If you think
that anyone sits and adjusts each radio for max output, for a $40 retail
product, you're dreaming, even if it's made in Pakistan.
On the high end, you MIGHT get this, but I rather doubt it.

Once you adjust anything internally, you've violated the certification.
These days, I'm not sure where the regs fall, but if you can have a radio
repaired legally, then it would seem reasonable that the same shop could
adjust it to as close as possible to the legal limits, legally..

But as others have said, you'll never notice the difference.
It really takes major improvements to make minor differences.
The antenna and feedline is the cheap and (sort of) easy place to make these
differences, and it's completely legal.

--
KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR