Thanks again for the info! If those pieces in the waste line and treated line were not flow restrictors then this unit does not have a restrictor on it at all and that doesn't make much sense either. I got all of this stuff at no cost so i'm not too upset if some of it does not get used. If the first TDS meter would only be reading the TSS from the sediment and carbon blocks then there isn't much advantage in me installing it. I'll toss the other one in between the RO membrane and DI as you suggested but i'll use the readings as more of a ballpark suggestion on when my filters start to go. I'll have to pick up a new handheld TDS meter and run a few tests. I think i'll put a better restrictor in the waste line and remove the two that are in the unit currently. that will likely help with my overall water production as well I would think.
Presently this unit is rated for 50gpd, do you see any advantages / disadvantages to me replacing the RO membrane & flow restrictor to 75gpd?