Cats or not, the o2 sensors are still needed. They tell the computer how much air and fuel to give the motor. If they go bad, your MPG will suffer. The computer will have no idea how much fuel to give it, so it will more than likely run rich.
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89 black GT, 5 spd
flex-a-lite electric fan
flowmaster cat-back + h-pipe
1 5/8 equal length shorty headers
MSD Blaster coil
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