headers vs manifolds on a 318 2bbl difference ????

I've seen a few videos where headers on an early 340 only gave small gains in hp.
Just proves hp dyno numbers don't mean much compared to actual performance.
It don't prove anything against dyno's, just that adding 10-15+hp across the powerband makes a difference, especially at lower rpms cause it's hard to make gains there. eg.. at 2626 rpm every 5 hp gain there takes a gain of 10 tq to make it. I just think were spoiled with the amount of power we know that's available to us that's just a click and credit card away.