For a performance upgrade your going to need to upgrade the whole exhaust, not just the muffler. The sticked threads at the top of this section contain all the information you need about the bolt on performance upgrades for your car.
And just FYI, our ECUs cannot be "chipped". They must be flashed with a SCT device with a custom tune.
'07 ST ; formally bewst'd
'86 XR4Ti ; 2.3L Turbo, 15psi
D23 Crew: #07