Yeah, I'd definitely like to see a dyno of the 3" vs. stock. Here's a dyno of a 70mm exhaust vs. a 3" exhaust on a measley 2.0L Civic SI motor. No tuning:
You can see that the 3" gains probably 5 whp up top, and maybe as much as 10 ft lbs of torque at the vtec crossover.. and it loses maybe 2 ft lbs of torque down low. That's with zero tuning. If a 2.0L 4 cylinder motor can benefit from a 3" exhaust, it stands to reason that a much larger motor such as the Z's can as well. Enough with the backpressure nonsense, we need to see some dynos!