Does my 2000 chevy impala need the residual pressure valve ?

my lines rusted out and I went and grabbed the parts real easy fix, except the residual pressure valve is really rusted in there, I can hook it up without it but will it make a difference,I know it's a anti siphon device but does it really matter and if so where can I find a stock cheap one all the ones i see on the web are all for " HIGH PERFORMANCE " which means HIGH PRICES when I search for a regular RPV there know where to be found // and when I showed it to the guys at NAPA (who are usually pretty help full & knowledgeable) they were like " W.T.F.is that LOL I didn't know till I looked up the braking diagram, but now at least i know the name can any one point me in the right direction thank you