So, I've wanted to install an AF ratio gauge in the mini, but haven't been able to bring myself to spend the $40 or so on a decent one (that looks like a "mini" gauge face).

Anyone know Why these are so pricey? And, any recommendations on which ones are most "mini-is"? Tia!

 

You're talking about a cheap one that you splice the wires into the oem sensor? Or a wideband kit? If you only want to see your A/F using the oem sensor, find a cheap one, if you want accuracy for tuning and safety, buy a wideband kit. I've bought an AEM Uego for around 200$ (comes with the gauge, wiring and wideband sensor).