My ball pump mix used to have 100 pounds of fine blend sand that's not available now so I think the sand is out of spec regardless of what the plant tells me and they want to add toxic vmo to avoid backing off a little bit of the half inch rock so what's the best answer.

I would demand your same mix or fine another suppiler a ball valve pump is a  special pump   once and operator learns how to prime and pump concrete, You might try it at their yard, we have 4 suppilers in town tow of them I couldn't pump, man stand your ground.

Yea I been scraping with them to fix  my old pump mix for today's application and test runs in the yard is what it takes for me to sell their product I have done 2000 yard of, the plant uses my current mix for sand finish.