Ok I have a 03 evo, now I first bought the hks ssq bov; car didn't like it even it's recirc. So I sold it, back to stock plastic. Worked fine. I used the money I got from hks bov for a greddy rs, it's recirculating so it should be find. Here’s the problem, after installing it, a few days later, I started to have this occasional rough idle. Whether I’m warming the car, stop light, or the car is just running for a while. sometimes it's working fine and the next time I stop, annoying rough idle as if it's going to stall the car. I adjusted a million times already thinking whether too hard or too soft but it still does it. And what the heck is this whistling sound while I’m cruising? I don't have cams (not yet) anyone have this stup!d, frustrating prob? If I get so pissed and can't find a remedy for this, I’ll trade for a stock metal evo 8 or 9 bov.

 

check your vacum pipes

check ur bov pipe

 

I would suggest a metal stock bov or a Forge RS unit which seem to work best

 

+1 to the forge, i have the 1g style forge valve and works perfect!

 

maybe the BOV has a leak and thats the whistle youre hearing.