I use copper oil psi line and gauge to measure hot side back pressure. This was suggested to me by my 'build mentor' The gauge bounces a lot until you pour the coals to it but I got nice steady reading at the upper rpm range this way.
I found out just how small my Ford SVO turbos were that way and moved up to some Precisions that have a much more friendly ~2:1 ratio (for my big heavy street car I'm fine with that in order to get the responsiveness I want)