This might be stupid but I pay attention to the power to weight ratio. I know it is simplistic to look at it that way but whenever I even think of doing a mod to the car I ask how much is it going to weight and how much more power will it garner. I try to keep the power to weight ratio around 7:1 . Its a really good goal to shoot for that but obviously other factors toss into to that. Some cars that are 8:1 run as fast as cars that are 7:1 and vise versa. I just look at that 7:1 as a healthy goal and try to make informed decisions to keep any extra systems out of the car if the really arent going to help that.