Hey all - haven't been around for awhile... 3 little kids and my machine has been running like a top! Well... until recently heard the safety valve start blowing off pressure a few times and watching the needle go past 1.8 bar.... ooops... Time for a new pstat again. I had gone through a few ceme pstats in the early years and then Chris of Chris' coffee service recommended a Jaeger pstat as a replacement. I had them check my previous order and it was in 2006! That was pretty impressive to me - 8 years! For some reason his site now says not recommended for ECM machines, but I have an original Giotto and it's working great - I think some of the new machines might have size constraints, but just check with them when ordering. Just wanted to pass along the referral in case anyone else gets into the same boat.

Just got through overhauling an ECM Giotto that had a Sirai installed somewhere down the line. A bit cramped, so replaced it with a Mater and relay as recommended by erics. A benefit of this is that it runs the 110V through the relay and not the control box.

I didn't want to drill to mount an SSR so I used a standard relay instead, as there are no heat sinking concerns. So far it's been working well, and takes up a lot less room than the Sirai. Pics in this thread show the installation - ECM Giotto Project

Are you sure you don't have scale build-up in the tiny passages of the PSTAT and maybe the PSTAT pipe? Have you tried rpavlis's method of using 50/50 vinegar/water and cycling it on/off? He uses vinegar instead of citric acid in this case to avoid deposits the latter can make in small passages. Of course the membrane may also have aged and Sirai even offers rebuild kits for that.