Want more power from your 2010 TC250 and a surprise from the Husky factory!

Dumb questions, what is it you guys are trying to achieve. Is the O ring hook up a sound improvement for a weekend trail rider. Should the end cap also be removed and what results should I really be looing for. One thing that wasn't raised was fuel economy-does this seriously impacted?
I think I fell into heap with all this techno stuff you guys know. Its comforting to realise that I am in good hand on matters Husqvarna.