When I first purchased my car, those coolant lines were still in place. I blocked them off just to see if there was a difference in performance and the way the car acted. Didn't put it on a dyno, but i couldn't feel any difference in performance. What I did notice, on a cool day on the way to the gas station in early spring (Temp in the upper 30's to lower 40's) without letting the car warm up the throttle body froze up and died untill i warmed it up with a friends heat tape wrapped around the throttle body for a while. If you drive your car in warm months only, block it off. If you want to drive it when it is cold. then keep them hooked up. Do what you want to. Just my 2 cents and experience.