very strange
do you live under the sea?
or maybe in a salt factory?
if rust is the problem then sticking a stainless system on should put an end to your exhaust worries forever.
a cat back system can affect performance for better or worse because i'm pretty sure bravo/as get some of the required back pressure from the cat back part of the exhaust. if you stick a wider exhaust on (with the middle box removed as with most of the systems i've seen) it will lower the overall back pressure.
that can play hell with your bottom end torque, but will give more top end power. overall it isnt a satisfying result on most cars. bottom end torque is almost always more important than high end power, even though peak power figures are all you ever really hear people talk about.
if you have a turbo, and you can create a custom ecu map, lowering back pressure a lot can be a great thing (running higher boost is possible). on an N/A car running a standard map it is rarely beneficial to lower the back pressure by more than a little bit.
from what i've heard supersprint exhausts work well, sportex ones do not.
