I ran my best 1/4 et with the seats in...thought I could better the et with the seats removed and I've never been able to do it. Also, the back rests of the rear seat carries the most weight...the bottom portion is light as a feather and not worth removing. I never removed the passenger seat along with the rear, but I do not think it would matter. Traction and a better than 2.2sec 60ft et is where it's at.