Welcome to the forum!
The Girard tankless hot water system is pretty dependent on water pressure...
Add a regulator that gives you 50 to 55 psi, and that'll go a long way to making it work better.
Another tip: set your water temperature at the temperature that you wish to use, and only use the hot water faucet.
(Don't try to add any cold water to the mix...)
Good luck!
Thor Forums
