there's so many threads out there on this topic. do a quick search for boost creep, it'll give you 11 pages or more of info. then, if there's still something you're unsure about then ask something more specific on this thread.
Looking at your profile, you have a 2.0L which doesn't get boost creep, unlike the 2.5L. Using engine management, you can maximize hp gains after adding an aftermarket downpipe. U-tec, Acessport, Enginuity, Tactrix cable are some of the most common engine management products.