the needle valve inside might be bad if its leaking, thats your fuel rail. so its leaking gas, capping it is not the fix. i ran for years with out one, it never leaked.

its just like a tire air stem, the needle valve comes out by unscrewing it, its o ring might be bad, or maybe you can make it tighter and seal it up.

id hit a junk yard for these parts.

no idea, on the race.