When I initially received my Magister Stella, I got myself a cheap pressure gauge and rigged up a my PF to test the max brew pressure... was sitting at a nice 13-15 bar, so I brought it down to around 8.5-9 bar. After a good while of experimenting, noticed my shots always lacked body no matter the temp/grind/dose. So I made a small adjustment up to 10 bar on the weekend and voila, I got the body I was looking for... fully aware that my gauge may be inaccurate, but my taste buds say this is the sweet spot (could be 7 bar for all I care!).

Now I've noticed that the grouphead temperature generally sits around 209-210 F vs about 204-206 prior to the adjustment (measurements on Eric's thermometer).

Really don't know how one can effect the other and this doesn't seem to fit the "thermosyphon stall" symptoms. Anyone ever experienced something like this or can help point me in a direction to figure it out? I'm aware that I can lower to P-stat, which will lower the idle temp, but I'm more curious to know if the OPV adjustment and idle temp could be related.

Not related at all. May have bumped something.

I agree with Joe in that brew pressure and grouphead temp are not related.

Increased room temp = increased grouphead temp and, of course vice-versa. Portafilter in = lower grouphead temp whereas Portafilter out = higher grouphead temp. The difference in either scenario is about 1.0-1.5 degrees.

What is your MAXIMUM boiler pressure (just when the heating element kicks "out") ?

Mind if I ask how you sealed the gauge to the portafilter? I am doing the same thing with my Lelit and I can't keep water from coming out around the top lip of the portafilter. Even if I use an empty basket. Its like the basket is leaking between it and the PF. Thanks

When you attach a pressure gage to the bottom of the Portafilter, you generate ~ 9.0 bar of pressure between the basket and the Portafilter edge. This becomes a metal-to-metal seal not designed to handle that 9.0 bar. So, as with the overwhelming majority of Portafilter pressure gage setups, use NO basket and you will be leak free.

DO NOT overtighten the Portafilter as it is not necessary. But, in addition, if the leakage you are experiencing APPROXIMATES the flow of a "normal" shot (35 ml in 30 seconds), you are then getting a more representative pressure reading.

I think I found my issue both my bottomless and regular lelit portafilters have notches by the handle and opposite. This means there will never be a good seal. I am going to try to find a 57mm with no notches I guess.

I think I have the solution. Attach the gauge to the blind basket itself. That way its just the basket seal and the notches don't matter.