Before I got my gauges, I called autometer on the same question. The guy there said that the autometer A/F gauge isn't compatible with the stock A/F sensor on subaru's b/c the gauge reads a wide band signal and the stock sensor is a narrow band signal.....or vice versa, I forget. Whereas most other cars run the same signal as the autometer gauge, hence no problems. So basically, to run an autometer A/F gauge, you need their A/F sensor also. Probably not what you wanted hear, but thats what they told me. The guy I talked to seemed pretty knowledgable and explained it pretty well to me, so I dont think he was taking me for a ride and getting me to buy more stuff. Hope this helps.