If one can not get a liquid filled gauge, a shutoff valve, needle type valve works best and a regular gauge, close it down until the needle is not jumping around but still reading and it will work fine. We do this to dampen the gauges on our Hpacs at work.
I havent checked mine and given they dropped the one I probably should check it just to be sure but it seems to be working fine.
Do espresso machines have a habit of straying after a while or is just a general good to do just to check thing?
Aaron