Be very cautious that you do not bottom the nut on the threads just as you are reaching the prescribed torque. Very often the insulator material in the firewall blanket will compress under time and or leach out if oil gets on it thus the bolts grip legnth will be too long.

To check for that scenario-- remove the holding wrench on the inside and make sure you can reach the torque value outside-- before turning the bolt. If you can--- add washer(s).