It revs quicker and also can go much higher with freeflow back box.
Exhaust manifold and 1st silcencer box are also those that are not very optimal, 4-2-1 exhaust manifold and new exhaust with good quality free flow boxes should give you quite nice improvements to how engine behaves.
Making also intake manifold to match pulses properly and we are starting to find engine from that piece of iron, that is if you already have good programmable efi and sensible cam there, I would think even K-cam is not very high performance part, just something engine originally should had
One thing, with injection model airfilter box you are effectively getting hotter air into engine, of course only when running slow, but still as air tubing goes over radiator + air filter sits on exhaust side of engine.
