mitsu brakes are notorious for warping rotors. many people with eclipse or
talon cars equipped with the single piston caliper upgrade to the twin
piston brake and it's larger rotor.  that is really the only fix we've
found.
the single brake piston seems to flex the backing plate and cause the pad to
unevenly contact the rotor.
that's probably not anything that will help you but that's a bit of history
with mitsu's brakes.
flex and the taper that is wearing into the pad will cause noise.  some pads
are quieter than others. find out what's available in a low noise pad for
your car.
i am using ebc greenstuff kevlar pads and there is zero squeal.

on my '01 eclipse spyder, the brakes were squeaking a year after, the dealer
changed the rotors, pads and calipers stating there was a recall.  2 weeks
later, same issue.  I popped the pads off, put anti squeal goop on the pads,
they stayed quiet for about 6 months, then started again, I regooped again,
no change.
So I tore the pads off, went to Autozone and bought their Morse Ceramic
pads, these are the best pads I've ever used!  Stopping is more firm, no
squeaking, they're just excellent pads!