It boosts low midrange torque. The chamber creates a resonance that boosts pressure at the throttle body at certain rpm ranges, thus increasing air flow there. I saw an article in some online mag several years ago that referenced it. Didn't have a dyno curve sheet but it stated that it was good for several foot pounds. Some of them are just silencers, but this one is for power. Same on mid 90's Miatas. Late 4.3 Jimmy motors had one in the manifold casting with a servo on a gate for it, also for power.

Some of my preference is due to living on granite, where the dust has a lot of quartz. If I was still in Alabama and on limestone, I might feel different.