Yes, they improved the pump. But, there are thousands of the bad pumps out there as old stock in the parts warehouses. Of course the price went higher.
Luckily I bought all the original design pumps my warehouse could get back when the problem started. My left turn guys insist on them.
NEVER run a hi-vol pump in a street engine. The pump will cause excessive dist gear/cam drive wear in many applications. I have been seeing a lot of this since the oils we are forced to use came about. Plus most of that hi-volume oil just blows by the pressure by pass and is wasted.
My left turn customers are known for using an engine up. Amazes me how much a rules built engine can put out, and they all use std volume pumps with a spring replaced. Or M55-A