The "Sniffle" valve on a fuel injected Lycoming engine is used to drain fuel from a flooded throttle body intake. The sniffle value is "open" when the engine is cold, and slowly closes as the engine begins to heat up. This keeps excessive amounts of fuel from collecting in the intake manifold during starting when flooding can occur.
I forgot to take a picture of the $60 sniffle valve "accessory" but its basically just a giant piece of brass with a NPT fitting on one end that screws directly into the bottom of the oil sump, and a hose bib fitting on the other. I'm not exactly sure why this valve doesn't just come with the engine since it seems to be a mandatory accessory.
Installation is pretty straight forward with one big exception. On the plans, it shows that the black rubber tube is straight and that the 80-90 degree bend is done completely in the 3/8" aluminium tubing. If you do it this way, however, there isn't enough clearance with the bottom of the cowling. I ended up with about a 40 degree bend in the aluminium tube and about a 40 degree bend in the rubber tube to get sufficient clearance. YMMV.
