Start with the regulator attached. Then check your flow inside at the kitchen, bathroom and shower. If it's too low, there is most likely a built-in. I'm in charge of water hookup, but DH is the pressure valve guy.
BTW, while you're shopping for the regulator, if you don't already have one invest in a volt meter....plugs into a receptacle that's very visible. If you get near the red area, you need to start shutting things off or change to the 50 amp adapter. Not a pricey item and for sure a necessity.