I have some really good torque wrenches- one is even made in Germany- which I will assign to the Porsche tool box. I also have some Harbor freight torque wrenches. I checked them against a certified wrench- and one of the cheapies was right on. Another was off 2 lbs and the worst off 4 lbs (50 ft lb test). That's a 4% & 8% error (I think).
So a 8% error on a 7 ft lb bolt is not much to worry about and probably factored in on the design. So I wouldn't worry about it.
