I’ve been frustrated with the strength of my DS so finally did some diagnosing. I have a ‘bulkhead’ tapped into the top of my tank, then had a reducer and 1/4" elbow screwed into that, then connected to my remote valve. Lots of places to cause problems.
I found out it was sucking in air from somewhere, and no matter how much pipe sealer I used it still did it. Finally I got fed up and ran one line from my valve down the bulkhead into the PVC pipe to the bottom of the tank, and holy cow did that make a difference. I did a housewash today and it was almost as fast as my old 4gpm.
Just an FYI if anyone is noticing their DS is less than optimal, check for air leaks.