you know what is funny. I had this exhaust on my redfire 03 when i got it back in mar 06. i dont really know if it was the m55 or m58, but i didnt like it. It was a little too quiet. So i too it off and sold it, i think i got like 350 or so for it. I got magnaflow now, but damn i had no idea that it was worth so damned much. Oh well. Why is it so much sought after?