JBtuned - Genuine Continental Flex Fuel Sensor 13577429
This is the sensor we prefer and what is used when we design our flex fuel full replacement fuel systems.
This product page is for just the sensor but we offer some add-ons to cover what you might need.
Flex Fuel Mounting Bracket <- Click for more details
Quick Connect Fittings - The fittings are what you need to set you sensor up for you 6AN return line. See Pictures
Flex Fuel Pigtail for Hondata - Give you a flying lead of wire with the appropriate resisters installed to work with your s300. This gives you 6 feet of wire to work with.