I had extractors and a 2.5 inch exhaust in my cortina ( which had a injected crossflow in at the time). I felt it actually lost power down low, and up top it didn't go much better than before.
Before I got it changed I had extractors and a 2 inch exhaust. BUT... with a worked motor in it the bigger exhaust was really good.
My recommendation would be to put extractors and a 2.25in system (if the motor is standard, and a crossflow).
Daily driver- EA fairmont ghia, ef motor, 5 speed, 3.27 diff, superlows- 120kw @ the wheels, 14.9@92mph
Daily builder- TC cortina XLE, waay to much to list here....