I dont knwo about those two TSB's, but when you say you're having a clunking noise when driving over bumps, it could be and sounds like a suspension problem. Doesn't sound like it would be a drive train problem or you'de notice it at other times, not just when driving over a bump.
How far exactly did you lower the car and is the springs listed in your sig. your only suspension modifications ?
I got the Eibach Pro System plus (springs, struts, sway bars) and no else supsension mods. Since the installation I noticed this clunk. The drop was about 1". I had the kit installed through a Mustang shop (what I heard it's a good shop) and had them check the installation again. Unfortunately I couldn't reproduce the noise with the shop owner in my car because the roads were too smooth around the shop. While I installed the mid-pipe and mufflers I could convince myself that everything was tight and nothing interferes with the movement of the axle. Rocking the car through the rear bumper doesn't make noise .
The fact that you stated you didn't notice anything until "after" the mods were installed and the fact it happens only when you go over a bump in the road still suggests something in the suspension setup. It could be possible that due to the lower clearance of the car, part of your exhuast might be hitting the road or some other part of the car. I've had this problem with my long tube headers and prochamber before. Might want to look the exhuast over and see if you don't see any scrape or scruff marks just to rule that out.
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