hey, thanks for the reply!
I initially installed their chevy/GM pump with the "lower rated 950 psi" and that one was horrible. (BTW, I am running a Firm Feel Stage 2 box).
Then I replaced it with a 6.1 Hemi p/s pump, better but still develops a whine and inconsistent pressure when driving for extended periods of time, like the freeway. Driving locally or for short periiods of time, no whining.
I am pretty sure I am running a 5/8" line, I forget. It is the line recommended/sold to me be St & Perf.
Thanks again!