It's true.
I am in a way encouraging @drftking247 's desire to mod his engine because in a way it is a learning process. In fact it will be a good lesson for him, be it may expensive or laborious, but in the end his satisfaction will be met by his efforts.
My life's lesson with engines is that, quote: there is no better feeling of satisfaction and confidence with the engine you rebuild/modify and tune with your own hands.
Going back to your 4K, I was once told that engines have reciprocating parts, and every piece of it holds an amount of rotating mass, once you lessen that rotating mass you get speed and acceleration but you sacrifice torque, that is when you weigh your options.