while i was fixing my dent and swaping interiors for a while i was driving without anything other than a dash and driver seat. i did notice the car felt a little faster. i was down at least 300lbs because i normally have everything back there even the spare and my heavy ass subwoofer box. i think it weight 3,3xxlbs when i weight it. so it will make a noticable difference. the big problem is it looks like shit, you can here every fucking little noise, and not one girl i know would ride in my car while it was like that. even if put the seat in. so yeah. waste of time unless you have a reason for doing it. there are a lot of things to loose if your not careful.