To everyone thinking about changing their exhaust systems, DON'T
The stock midpipe is the correct design and changing it to bigger or smaller will result in a power loss.
The problem with almost all shops that make fabricated exhausts is that they don't have a dyno.
customer: lalakas ba hatak pag nagpa exhaust?
shop: oo naman boss
customer: gano ka lakas?
shop: ewan basta lalakas
lalakas sa gas is more like it because you will have to step on the gas more to get the same power before you put an exhaust.
here's a dyno chart of a mirage that had a fabricated header and exhaust done.
blue line: stock
green line: speedlab intake with fabricated header and exhaust
red line: speedlab intake and header and stock exhaust
Notice a drastic dip in hp from 2000 all the way to 4500 (where your car spends most of the time)
The torque loss is even more dramatic, losing 12ft-lbs at 2000 rom, resulting in a loss of hatak.
Now as for the every present question of "what muffler should I use?" The answer is it doesn't matter, as long as it's just the end section, the size can be anywhere from 2-2.5" inlet. Mufflers add zero power BTW
So moral of the story, disregard everything you have read in the first 9 pages of this thread, do not change the midpipe, do not change the resonator The proof is right here