cat-back
#2
a good performance cat back is usually good for about 15 hp. I dont know the specifics of the dynomax system but I believe they are on the cheap end. You probably have a similar increase in power but with less durability and more noise. There are probably people more knowlegable that can help you out. Since your car is a 6 speed, if its in good shape it should be putting out around 300 to the wheels + the exhaust.