When I got my CFII, many moons ago, I went to the FAA for the ride, as finances precluded me using a DE. Anyway, this particular inspector had a reputation for being a d**k. On the oral, after about two hours, he asked me how the attitude indicator re-erected itself after a tumble. For the life of me I could not effectively explain to him how it worked. That was the one and only ride I ever busted. After about two weeks, and the requisite re-training, I went back to this same guy. That was the only question he asked me the second time around. I answered, almost verbatim, out of the Instrument Flying Handbook. We were in the air after 15 minutes. The rest was a piece of cake. Sometimes, even then, they like to put you in your place. Make sure you know ALL the details! Good luck.