looking on their web page I can't see any of their pumps rates to 2800rpm ?
(just moved, so internet via mobile phone right now, bit slow, maybe I missed some?)
either way, gear pumps flow rate is pretty flat as pressure increases, so flow rate with no pressure shouldn't be miles away from flow rate against pressure
but... the front section of the pump with the gears in it looks quite long to me... and has pretty large ports, 1inch? which would make me think it's higher flow rate lower pressure?