Hey! While were talking about this...
There was a thread or two earlier, about a similar noise problem, but I seem to have lost the threads' subject title..
Came across several times Michigan/Indiana roads have gotten the best of my Strut Tower mounts...
Referring to these guys...

The "puck" on the right, is what comes out of another tower you bought with the Ford S or SE series, that is a polyurethane bushing that the struts' main shaft bolts to.
What occurs, the vehicle strikes the pothole - the wheels attempt to absorb the impact, but in turn transfer it to the strut, the tower and eventually this mount - if you hit it hard enough or often enough, these pop out of position and float about ABOVE the seat - the one on the Right is the results, a hockey puck...
The one on the LEFT is the SAME Mount and flange system - it's what it's supposed to look like.
Note the "card" below - that number is what I use now - it's for the ST series, but the mount seems to hold up better and is a slightly different composition than the OEM one you get.
Now my "experiment" is still ongoing but in using this "idea" with the roads and their condition, this is going to be an ongoing - many peoples' problems, with the Fiesta - its' not built for OFF ROAD as the typical Rust Belt roads are turning into.
So I have done more work than this and as time allows I will post some of this work so you can try it yourself - let's just say I'm working on a backing plate to keep the strut bushing in place - I'll give you folks a post about the results as spring and Pothole Season comes to a close and Summers' Road Construction season begins.