AV1-12 is the std air valve with black fluro-silicone diaphragm, AV1-12-2 is the same but with a yellow Silicone diaphragm I would revcommed it as silicone seem to respond better in cold climates. AV1-12-3 has a leaner cone on it. Make sure your vaporiser does not leak with the engine off by removing the hose and and taking soap solution to form a "bubble" across the end of it, If the bubble grows or pops imediately the vaporiser is leaking thru and will need to be rebuilt, You will need to apply vacumn to the VFF 30 to make sure the vaporiser is under pressure though. You might also remove the air valve and inspect the cone seat inside the mixer, if it is cracked OR out of round replace the mixers as is is junk

jim