I need to find an aftermarket digital fuel mileage gauge. Any ideas?

 

Most anyplace that sells aftermarket guages would sell a flow meter.

 

Autometer Nexus series. I have this in my S4, I have the boost, EGT, AFR, and IAT, gauges. I searched for a longtime to find the best in the business, this is by far it.

http://www.autometer.com/demos/nexus/

Best web-site to buy gauges IMHO. Extremely helpful guys if you call them.

http://www.egauges.com/vdo_main.asp