I actually don't have the HFM installed either. I put the CAI on so I could compare the power difference once the HFM and Conforti chip were added. But man, that CAI sounds great...;/ Can't wait to add the HFM and chip tomorrow. Actually, to accompany my modified stock ///M exhaust I'm also going to be adding a complete custom - dual stainless straight section to replace my catz as well..... I'll post my reactions- Ryan- 95///M (subtle yet vicious)