Its pretty simple. You lost torque by having an exhaust that decreased backpressure to the point of losing power. That is why unless you turbo your car or have some other type of forced induction you do not want a big exhaust with no cats. you lose backpressure and therefore lose torque. Easy and simple as that. The STX is the same as ST but if you take an STX vs. an ST with minimal backpressure which causes torque loss....well then your ST is slower. DER!
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