If you are looking for a carb version of 20 PSI and less it may be a trick to find a digital one. All the ones I see are designed for upto 100 PSI ranges which usually means they won't be very accurate in the sub 20 PSI range. Being 2 PSI off is not a big deal in the fuel injection world, but is in the carb world. Personally I would use an isolator to keep a mechanical gauge.