first welcome to the site, there is no part that you just "add", you are probably reffering to the fuel plate, to get extra power, you can do a few things, first you can slide the plate forward which will give you more rack travel in your pump, allowing more fuel to go to the engine. the second is that the fuel plate can be taken out, and modified, by either replacing it with one that is already a "performance cut" plate, or modifying your stock one with a file or dremel tool. do a seach on the site, and you will turn up alot of information.
wes