Everything I've read about the s197 v6s say that dual exhaust doesn't free up any power. Not even for a boosted app.
CAI and tune are where it's at. Blower if you can swing it. The dual exhaust is nothing more than a noise mod.
There are a couple exhaust setups out there that claim to optimize exhaust scavenging for the v6 but they're single exhaust setup with LTs, free flow cats, and a different cross over tube.
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