I bought a used carb that has been bored and has a velocity stack on it for my 08 YZ450F. The carb has a NCVP needle in it. I am not sure what all the letters mean. The manual shows optional needles for richer or leaner and this not one of them. I know the last letter is richer or leaner and I believe the 3 letter is where the taper start but i am not sure about the rest. I am also trying to find a air intake boot that will work on the velocity stack. I was running PVC pipe to a universal K&N to get me through the end of the season and that the guy I bought it off of used when he ran it. I have seen other bikes with a velocity stack that have a OE style intake boot but i cant find what they come off of. The OD of the velocity stack is 62mm. This bike is used for flat track racing.