Absolutely the parts gain power without a tune!
We choose to show off the 3.0" system with a tune as we feel that this is the natural progression for the customer. They buy an exhaust, buy an intake, and finally buy a tune. We want to show that the 3.0" system will make the most power when the customer gets to that final stage.
As we have shown before, the bolt ons add power without a tune. Here is the 2.5" catback system with NO tune.
Showing the HP gains using the same ECU tune between runs shows that the 3.0" system makes more power than the 2.5" system. That is the important thing to take note of. This shows if there was a stock tune on the car, that it would be same thing, the 3.0" system would make more power.
Above is an example of the same tune used and just the header back exhaust was changed. The stock ECU tuning isn't so limiting that the 3.0" exhaust won't gain power over the 2.5" system. Our goal with showing these graphs is just to prove the 3.0" system doesn't lose power but gains power over the 2.5" system.