This is totally open for debate and I don't claim to be the expert here. I would like to actually dyno this to see what happens. But the reasoning is thus.
1. Our V8 engines at WOT, in the lower rpm ranges, (say 3000-6000) seem to make a lot more torque with collector extensions than without. The only testing I've been able to find on this is with open exhaust.
2. Using collector extensions is a wave/scavenging effect, not a flow rate thing.
3. The wave tuning will happen when there are significant/abrupt changes in diameter
4. Since it's a wave tuning property it stands to reason that it MIGHT also hold true even with an exhaust system connected
5. (Unrelated to power but very important for cost control) Having a collector extension connection allows easy hookup to different header collector diameters and locations.
