Whenever you remove system modifications, they must be removed completely, and the only way to do that is to use the uninstallation tool, if any, provided by the third-party developer, or to follow his instructions. In some cases it may be necessary to re-download or even reinstall the software in order to get rid of it. I can't be more specific, because I don't install such things myself.
Here are some general guidelines. Suppose you want to remove something called “BrickYourMac.” First, consult the product's Help menu, if there is one, for instructions. Finding none there, look on the developer's website, say www.brickyourmac.com. (That may not be the actual name of the site; if necessary, search the web for the product name.) If you don’t find anything on the website or in your search, email the developer. While you're waiting for a response, download BrickYourMac.dmg and open it. There may be an application in there such as “Uninstall BrickYourMac.” If not, open “BrickYourMac.pkg” and look for an Uninstall button.
If you can’t remove software in any other way, you’ll have to erase your boot volume and perform a clean reinstallation of the Mac OS. Never install any third-party software unless you're sure you know how to uninstall it; otherwise you may create problems that are very hard to solve.
Trying to remove complex system modifications by hunting for files by name often will not work and may make the problem worse.