How much will adding 16 lb to my car affect ET/mph(rotating weight)

The old rule of thumb is 100 pounds = 1/10 of a second.
True, but that is for static weight. The more weight that has to be rotated, the harder it is to accelerate that weight. Its a lot harder to accelerate a 60 lb flywheel, than a 12 lb one, for example.
I will admit, i dont think 16 lbs at the wheels would be very noticable.