Please check the tightness of the bolts securing the 2 diagonal struts between the suspension upright and the engine bulhkead.
I was puzzled on hearing a thump in my E85 everytime i reversed out of the driveway. Then the thump can be heard whn oing over speed bumps. It sounded like something was hitting the body especially if one of the front wheel is loaded up.
My mechanic and I went thru everything underneath the car, we tightened all bolts, supension links and engine mount. It was finally traced to just one loose bolt on the strut at the bulkhead.