[purplept]

I agree that just adding an exhaust system doesn't necessarily increase engine performance. I believe upgrades have a relational effect. For example, adding an exhaust system on the PT without doing anything else, has little if any performance advantage. However, when combined with other upgrades such as air intakes or a Stage kit, then the exhaust upgrade has a performance benefit related to the other upgrades, i.e., more air in, less restrictive exhaust out. This can be collaborated by reading the fine print on Mopar's website where they indicate that the horsepower and torque benefits on the Stage 2 and 3 kits for the SRT4 are fully realized when using the Mopar/Borla exhaust upgrade. However, on some cars such as the Subara STI, a catback exhaust upgrade can add up to 38 horsepower. I've done exhaust upgrades on two PT's, one N/A and a GT and can't feel much of a difference until upgrading the intake. But, the Mopar dual exhaust sounds and looks very good. I like mine.