The most drastic increase in power, outside of a full exhaust, I've experienced from a single mod has been a port and polish. If you're not comfortable doing it yourself KOR will get you set up with something you or I couldn't compete with anyway. LOL I've not done it just yet, but I'm told KOR's chamber reshaping is pretty unreal as well. The port and polish will cost you time and Dremel bits, and the chamber reshaping is less than $100 shipped. I can only speak for the port/polish and it's pretty salty even staying on the mild side of things.