I just did my springs and struts and replaced the isolators with the bbk ones. I had no choice for the front, the bottoms were destroyed. Compared to the stock ones its really hard to tell performance wise considering I did the whole suspension. Rides like a dream, but like I said that could be the new struts and springs. Id say replace them if they are broken/dry rot like mine were, the bbks will outlive the car no doubt.