hello, i didn't see this when i searched the forum, so i'm sorry if i'm covering old material. i'm considering buying an 05 mustang. v6 manual. upon driving it i've noticed that the clutch knocks, only when the pedal is pushed in and only when the car is moving. (ie: coming to a stop with car in gear or out and pedal pushed in) it is a very rythmic knock that slows down and stops as the car slows and stops. does not do it when the pedal is out, car moving or not. it has 99k miles and i know that the slave cylinder was changed about 50k ago. other than that its fine. shifts great, no grinding or sticking. thoughts? opinions? worth buying or major fix right off the bat? thanks in advance for any advice on this.