Gene Berg's take on gauges:
I loosely follow that, I prefer an indicator light over a gauge. Buy the switches at the pressure or temperature threshold that would concern you and hook a light to it.
Where I work we instrument our testing of turbochargers and engines for data acquisition. We have no automotive aftermarket type gauges. They simply won't do the job. We do use mechanical gauges on some variables. Those are supplemental to the D/A system and are only for by-stander reference. These we generally source from McMaster-Carr and only buy their liquid filled, small tolerance versions.
For EGT's on a turbo diesel I would look into using a Type K thermocouple with Swagelok or similar fittings, and find a decent thermocouple reader.
I used to swerve around my hallucinations, now I drive right through them.