I recently got my cat-back system installed with a glass pack. From what the people told me, this thing is like a muffler turned backwards so the sound is like you dont have a muffler and hp gains are better than with a muffler. I went to the shop planning to install my Apexi N1 which i heard was a great muffler for the WRX but ended up gettin a glass pack which was alot cheaper and nicer sounding imo. does anyone else have a glass pack? or no any other things about these?