I'm pretty sure high flow cats have dyno'd much higher than just just 5whp whether it is 8whp or 15whp or somewhere in between, opening up the biggest restriction in the exhaust is going to produce nice gains under the powerband and improve driveability.
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2011 370Z, 6-Speed Manual, Sport Package. - K&N Drop ins | Top Speed Axleback | H&R Spacers SOLD
2009 G8 GT, 6.0L LSX V8, Rotofab Intake, ARH Long tubes, SOLO exhaust, VMS Tune - SOLD
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