Originally Posted by Stangonline

It is truely about backpressure and velocity. Velocity helps scavenge exhaust gases - and if this can be achieved (higher velocity) at lower RPMs, then you will increase your power/torque in those RPMs. At some point (higher RPM), the exhaust size that provided that higher velocity down low will become a restriction, limiting peak HP. Because drag cars go for peak HP and typically have a narrow target RPM that they achieve that HP - they just go uncapped and do not worry as much about velocity except for what they can tune with their collectors.

Manufacturers are hunting for that perfect solution, where they can retain low end power and still have great high rshared_pm power. They are using the technologies that I mention to achieve this. Unless we use the same technologies, we simply have to install the parts that lean towards the cars intended use...been this way for a LONG time

So for this guy (and most street cars), a full exhaust will give him more torque in the RPMs where he spends the most time. Yes, he will sacrifice some peak HP for this compared to longtubes and open exhaust.