As the exhaust gas moves through the chamber it cools so it can move through a smaller hole at the end. There are two effects, sonic and gas flow. The resonant chambers are absorbing the Sonic energy and dissipating it. The small hole is plenty for the gas flow at a constant rate with reduced energy. Even performance pipes have a greatly reduced stinger, not exactly the same thing but it's similar.
I've built a couple stock exhaust maxis that went 35+ (one was over 40 with high gears) ditch the head gasket, run the 14 carb, mod the exhaust, 16*45 gears, a little bit of porting can do wonders, but the biggest gain is making sure that the bing gets re-tuned to the correct calibration for the 2 hp parts. I think they run better with a stock filter that's been derestricted so you can use the stock tuning parts. If you ditch the stock filter the atomizer and slide will be way wrong and it can be hard to find the right combo.
Bings are kinda touchy, even a little bit off and they will have a huge loss of performance.