I'm with Moose - something must be restricting flow somewhere?
Do you have an inline strainer before the pump? Don't feel bad neither do I, . . . yet.
By the way, I'm idling @ 18 - 19 and @ WOT 16 - 17, w/Comp on 5/4. Happier than a pig in slop

, I deserve to be after 5 POS Carter LPs bit the dust.
Did you call Rich @ Glacier? If not, give him a call. He'll give some ideas / put you in the right direction.
Is it possible the straw is too close to the bottom of the tank?
Huummmmmm? I wonder.
Don't feel bad, if you have to take the tank out again - I've had mine out twice in the last 2 months

. Once to install the draw straw and then again a few weekends back to install new brake line. With my eyes closed now - unfortunately.
Good luck - let us know what you find.