Have a '93 Mark VIII. Just completed the suspension conversion on front and rear. What a difference. However, now I have a problem with the brakes. When I press on the pedal, you can hear a hissing sound like air is escaping, and the pedal is hard to press and pushes back. I have to push very hard to slow and stop the car. No leaks have been noticed, and the brake reservior is full. Note: The car has had new brakes, rotors, calipers and pads within the last six months. I have been told this problem is a bad brake power booster. Anyone have any ideas or suggestions, or had a similar problem? What about installation, do it yourself or mechanic job?