hmmm....makes sense now.
It says 3 bar on the side, but I could only measure 2.5
Either the FPR went 'soft' (which they don't really) or something else was dodgy. But the figures with/without vacuum make sense now.
....The Vaux 'tuners' from southampton had fitted an adjustable FPR in series with the stock one, but had NOT adjusted it!!!
It took 3 turns (!) to see any increase in fuel pressure over stock. I was assured (2 years ago) that it was 1 bar over stock. It never was. The adjusting screw is tight too, so it couldn't have come loose either.
There was this horrible kink in the fuel pipe after their FPR, which probably accounted for the increased FP. Once that was fixed with a proper pipe, the FP dropped down to stock again!
A totally kinked fuel return pipe is a serious fire hazard, by the way