In all seriousness regarding a 400kw car, it is an expensive project, and if you do t do it all at once, the car can be off the roads for weeks at a time. I'm in a state of "ignorance is bliss" regarding the cost of my car, but IF I was to do it again, I would budget 20k. My signature has all of the weak spots covered (I hope) to get to 400kw, and stay there safely. Did the diff need to be done? Probably not, but as a whole package, I felt it was needed.