Way motor works carries the power flex bushings. As for stiffness I'd say it is stiffer than stock but its by far a more stable ride. I didn't heat the old ones. When I pulled the control arm off all the rubber from the bushing stayed on the control arm leaving just a metal sleeve in the carrier. A sawzall made quick work of getting it out.

 

Actually putting in the Powerflex is easier. The OEM bushings have to be pressed in at the right angle or they will wear out even faster, and the metal sleeves are harder to press.

http://www.waymotorworks.com/powerfl...shing-kit.html

We never recommend heating them with a torch as that is super dangerous.

 

Here is a video of the install. At 3 minutes it shows what you need to make in order to press the new bushing in. A little trick I learned was as you tighten it down the bushing wants to go in crooked, that's OK just take a c-clamp and crank it down on the side that isn't going in and alternate between the bolt and the clamp until it starts to go in. Then take the tool off and use a rubber mallet to hit it into place. The BMW tool has a sleeve that guides the bushing in but 125$ for a tool you only use once is a waste of money.