found this on the site that shall not be named.....
not mine just copied and pasted.
"After having some issues with my hydroboost I did a little research and on one post that Van wrote he said that the return line off of the hydroboost needs to go direct to the reservoir as to have no back pressure at all. I had my steering box and hydroboost tee'd in different ways with a cooler and I didn't get it working right until I ran the hydroboost return straight to the pump. I put the cooler inline with the steering box return line and then tee'd that into the hydroboost return line. Better yet is to have 2 return ports on the pump reservoir."