Just for your info...if you do a search for these questions, you'll likely find tons of informative threads which will give you not only which ones free up more hp, but also which one sounds like what.
and a tip: if you're looking for hp gains...what's a heat shield really gonna do for you. With an exhaust, it's not like your car is gonna come any closer to beating an E46 or an E36.
did anyone see the monster garage where jesse james cuts open the top of a flowmaster muffler..takes out all the restrictors and welds the top back on and installs it. Its basically having like not having a muffler at all..thought it was cool. sorry ot.