The 1650 goes with the 1650 injector assembly. I would ask the person who bought it to swap the injector system out to the correct size for a 13" tank, which would be the 1650 series, not the 1700 series. The BLFC on your current 1700 is 2.0 GPM. The 1700 uses the same buttons as the DLFC on your system. So in theory, your BLFC (brine line flow control) could be swapped out to a .6, .8, 1.0, 1.2, 1.3, 1.5, 2.0, 2.4, and so on. The 1600/1650 uses a much smaller button and is available in .125, .25, .5, and 1.0 flow rates.
For the drain line flow control, I would recommend changing that to a 4 gpm button. The current button (5 GPM) will work, but is a little higher than needed, and the smaller button may assist with the noise issue. Then again, it may also make it worse. It wouldnt hurt to try.
Hope this helps.
If you are in the Los Angeles area, I know a lot of local service technicians that would be glad to help you out for a very reasonable rate.