I am unable to test out in the NID the tech that hooked up our Internet just threw a bunch of wires in there and the Splitter got water in it but after I reset my router my margin dropped and my upload increased.
They should not have a problem replacing the NID if it is old. When we moved in they installed a NID from the stoneage that came with its own prehistoric critters. My circuit was always dropping out, finally convinced them that the NID was the cause of my problems. Cleared up a lot of the drop outs and noise on the line when they replaced it.