Correct me if I am wrong but the new 08 VRS have O2 sensors. I would think this would make things ez'er when it comes to slip on pipes. I thought the O2 sensor adjust the air/fuel mix as needed. Hence you change mufflers add better airflow on top and the sensor sences more O2 and richens up the mix. I am sure it has a limit however when I did this kind of work on a carb, it was only a few jet sizes bigger. Come on all you self wrenchers, lets hear it.