Well, I don't know about "Vast Knowledge", but thanks.
I typed "Headers work on
Reversion".
No They Don't!!! TYPO alert!!!
In a nutshell: The exhaust pulse leaves the cylinder, past the exhaust valve, out the exhaust port and travels down the primary header pipe. When that pulse hits the Header's Collector, something called
RAREFACTION occurs and a reverse pulse bounces back towards the cylinder.
If the size of the primary pipe is correct (particularly not too big), the pulse will arrive right on time to block fresh fuel from leaving the cylinder during overlap (when the piston is chasing the exhaust valve closed and the Intake Valve is opening to let in another gulp of fresh air and new fuel has entered/is entering the cylinder) via the injectors. Of course we want to keep as much of the combustible air-fuel mix
inside the cylinder.
Sidebar: At low rpm (idle), valve overlap (both valves are open) there isn't yet enough rpm/inertia to allow intake air to fully enter the cylinder without some being pushed backwards into the intake manifold creating the rough-idle "sound" a bigger cam is known for.
I hope this heinous mistake hasn't ruined your day and please accept my deepest apology.
I will refund your money, in full, at my earliest convenience.