Upgrades avenge x .25

I've seen some people talk about a power plenum and an upgraded reservoir? I'm just curious what those upgrades bring to the table? I'm not looking to upgrade mine. I'm happier than a puppy with 2 peters with the way my Avenge-X. 25 performs. I've just been doing some reading and was just curious. Once again thanks for all the feed back. Greatly appreciated.