Yes I know ista and inpa, the Torque Pro runs on the head unit full time so you don't have to run a cable and it is just an informational app that about 90% of us use in our BMW'S and I use a Foxwell unit when I want to do deep scans and or maintenance (it's so much better than ista-d.

As for the cap BMW used to use a lower bar/psi cap and for some reason (temperatures they wanted) they went with a higher bar/psi or else the coolant would boil, but as it stands with your new lower temp thermostat you don't need the extra pressure so going with a lower pressure cap will slow down the wear and tear on the whole system especially the expansion tank. Hope I've explained it well enough to help you on that reason.

Now your lower temp thermostat should still be getting warm enough to not cause any codes and if it is, then you could have a failed open thermostat just installed or not sometimes things fail even when new.

Did you clear all codes stored/pending? No intake implausible readings?(can cause your symptoms I believe because numbers don't jive in the PCM powertrain control module/DCM)

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