I installed Steeda underdrive pulleys on my 08 Mustang GT a month ago, and I'm happy with them. They free up a few horsepower and make your accessories last a little longer. Seat of the pants is a notoriously inaccurate measure of power driven by confirmation bias. Nevertheless, my car does seem a little stronger. I was expecting a small improvement in fuel economy, and it's possibly in the 1/10 mpg range. The engine runs smoothly. It's winter in Michigan, but the temperature has never moved above the normal operating range. The generator is fully charging the battery. The power steering feels the same. If you're concerned about cooling, perhaps you should hold on to your old water pump pulley. If you have a problem, you could reinstall that pulley and run a shorter serpentine belt. The new water pump pulley is quite large. There have been no leaks and no problems so far. Much easier to install from above the car than below it. If you move the air intake tube and the coolant overflow, there's adequate room to work. With a manual transmission, leave your car in 5th gear with the emergency brake applied and chock your wheels. In lower gears, the torque necessary to remove the balancer bolt was moving the whole car. I used a 15" breaker bar with a cheater pipe to loosen the bolt. The OEM Tools 7 ton puller from Autozone absolutely will not work - it's way too long to fit between the balancer and the radiator/fan. A Ford dealer mechanic let me borrow his Blue-Point®/Snap-On YA6490A, and the balancer was much easier to remove. The directions said to apply "a dab" of high temperature silicone to the keyway on the balancer. There was a lot of silicone on the key and the old balancer, so I scraped and brushed it off as best I could and applied a healthy dose of silicone to the new keyway. I don't think it's there to keep oil in the engine. The crankshaft front oil seal is there to keep oil from leaking out. I speculate the silicone is there to keep water and dust from migrating past the balancer in toward the engine. Installing the balancer definitely required a cheater pipe for the last step. Belt tension wasn't enough to hold the water pump pulley in place while loosening and torquing the bolts. A drift punch through the pulley hole around 8:00 kept the pulley from turning. You might also try rotating the tensioner counter-clockwise to increase belt tension. You have to remove the stud at 4:00 as you look at the generator. The snout has a 5mm hex on it, and it's easy to remove and replace with the bolt in the kit.