Donnie's GTS

Well, I'm not new to fords, been around them my entire life, but I have never gotten into the after market venue that is offered for mustangs, since I now own one I want to know what is the least expensive and most efficient way to gain the hp that I should be getting. To be specific, my stang is an 01' Bullitt, which already come with some upgraded parts that the stock gt does not come with, such as the pullys, dual 57mm intake, and higher flow exauhst, and it is only pushing 5-10 more hp than a stock GT, I want to know how to get the 40 extra, with the existing parts, so I can get up to or more than 300hp.

thanks,
jim