I've never seen any credible evidence that the ARV does anything performance-wise. Lots of evidence that it's there to help more exhaust gasses get into the intake via the EGR valve, so that's what I believe it to be. It will eventually start to leak and create a whistle/lack of boost. When I disabled my EGR I left the ARV because I didn't know what it was at the time and got horrible mileage. Shimmed the cover so the valve won't open and the mileage has been great ever since. So, I don't like it. YMMV.

Also, next time just make a new thread instead of bumping an old (and not very helpful in the first place) one. Looks like rwthomas1 hasn't even been on this site in over five years...

-Rog