Too subtle you think? :) I'll try again.

Filter mats are what I would call a mechanical filter. They remover particles from the pond water. Although they also provide a surface for beneficial bacteria to grow, they would not be my choice for a biofilter. The mats have to be cleaned. If you use chlorinated water to clean them, you will kill the bacteria. Even if you use pond water, the bacteria will still get disturbed. If you add something like plastic bottle caps, perhaps under the filter mats, they would provide a surface for the bacteria to grow. Since the bottle caps would not collect dirt, you would not have to clean them and disturb the bacteria growing on them. Bottle caps are just one of many materials that provide a surface for bacteria to grow. I use plastic balls and nylon webbing. If you do decide to purchase a UV system, be careful not to underestimate the wattage of the lamp. If the lamp is not strong enough, the UV will not function correctly and you will have to purchase another one.

I'm guessing you mean the flow rate at faucet #2 is reduced? Even if you have a partial blockage in that line, the pressure should remain the same. Remove that fixture and test the flow rate of that line. Could be just debris or calc build-up in the faucet assembly like klem1 said.

L'Anda Johnson You are correct, there is something wrong from the street up to and including the PRV. So let's talk about odds - places to look: The most likely places for a restriction is someplace the pipe narrows down already. Those places would be: 1. The shutoff valve at the street 2. the shutoff valve before the PRV 3. The PRV Clearly you want to be sure that the valves are all the way open as Weedmeister suggested. You may want to close the valves you have access to and re-open them (again, only the valves upstream of where you measured your pressure). Sometimes if there's significant crud blocking the valve you will feel it as you close the valve. Closing the valve can sometimes break that up and cause the crud to flush through when you open it up. I know you want to rule out the PRV because you replaced it... but if the valves are open THE most likely place for this problem is at the PRV. More specifically, there is a screen on the PRV inlet that can get clogged from debris because this is a new line. Be sure to rule out the screen on the PRV - simply because that's the most likely source of the problem. You said that this was new construction. Was the water service line new (new development) or was there a house there previously and you re-used the water service line from the street? This is what a PRV screen looks like: