Forgot about this, it was a while ago!
It was more of a hardware than software question, but using current version of software, and the question was not due to seeing something we'd done, more what we might need to avoid for unreliable or unpredicted results (and the time spent tracking down our stupidity!)
I think the answer lies in the method of filtering (Zooming) in the WPS500X, and in all likelihood the delay will be meaningless/negligible if any?
So the only question is related to step changes in pressure so where the system being measured moves from say 45bar to 38 bar quickly, as to how that would be shown on the trace, before re-establishing a zoom at the new pressure level ...?
Odd questions I know, but hey, someone has to be odd