QUOTED FOR TRUTH
Originally Posted by MrHarris
Should be 2.5" going to 3" will lose major torque.
You'd be surprised how many people don't understand this basic principle.
I see some brands that use 3" exhaust piping for the x-pipe section. An exhaust pipe diameter that size (on our car), will lose a lot of low to midrage torque.
Yes, it reduces the back pressure restriction, but unfortunately it also KILLS the velocity of the exhaust gas flow.
2.75" is about the max for exhaust pipe diameter on the S65 engine.
Anything larger than that will kill your exhaust gas flow...and your low end torque will drop off a cliff.