RaceRender seems to treat Speedometers and Tachometers specially but lumps most everything else into a generic "Gauge" category.
Under Display Objects, if you click Add, and then in the pop-up that comes up, click on Gauge, any of those would likely work. In the Display Object Properties, you'll need to choose the Field that corresponds to your boost (this is the most important part). You might also need to mess around with the Range in order for it to look like a reasonable range (but I think RaceRender generally does a good job of selecting the appropriate min and max; for my Fiesta ST, I get somewhere between -11 and 20 PSI). You could really choose any gauge, even a speedometer or tachometer, and as long as you choose your boost Field, then it will display that data (but there may be additional work getting everything to look really nice).
If you feel like making it look really fancy, you could even set the background to be an actual picture of your car's boost gauge and use the
Gauge Designer to
get everything to line up. That's how I made mine here:
https://forum.hptuners.com/showthrea...ta-ST-Template