There was a Napa Gold 3231 fuel & water separator in the spares box when we bought our coach. I have searched online to try and see if it is supposed to fit our ISC 8.3 Cummins, but no luck so far. I thought it was a spare for our coach, but when I changed the fuel filter awhile back, I took the Napa 3231 out of the box and noticed that it was a lot shorter than the...