94 is correct. The actual FBI investigators are a political. But the attorney supervisors who are good and lean R aren't going to want this. No one at that level of expertise is a political. I would anticipate that most of the experienced attorney investigators will be D's as no R attorney in that town would take this job. Mueller though makes the calls and the actual investigators are FBI.
I also guarantee you that Mueller could explain each and every hire without reference to their donation history.