So what performance do such systems add? 
I have never really noticed a performance change after upgrading the exhaust on any of my previouse cars. However, I really noticed an increase in power at take-off and on the highway on the H3. I was very surprised and a I recommend the upgrade! Sadly that is gone now due to 35's, I felt a big change after going bigger. I am wondering if I have the dreaded head problem, becuase it was a bigger change than I expected.