Stillen exhaust - gain vs loss?

Originally Posted by FricFrac

I've got my Stillen Cat back, high flow cat and G3 intake on order however I do have a question about the cat back exhaust. I know Stillen puts a lot of research into their products but the cat back exhaust is about 40 lbs heavier than stock. Isn't that the equivalent of loosing around 4 hp from the additional weight? So while the gain on the dyno is around 18 hp the net effect is about 14 hp? I guess the good part of the weight gain is that its below the COG....