hrmm u shouldnt have engine noise then. take some sandpaper and sand some of the paint under where the seat bolt is to get a better ground. also, are you running the same gauge wire for the ground as you are for the wire going to your battery (i also hope you have an inline fuse on your battery wire for your amp. if not GET ONE)? if not you need to. also, you dont need to have a long ground wire going from your amp to where you are grounding it at.