1. I have a Forge vent-to-atmosphere (VTA) compressor bypass valve (CBV). I have no issues with idling and stalling at all.
2. If you want to spring for an MR CBV, then more power to you. It works just like the stock GS-R/RS CBV. So you won't have any issue with idling and stalling. The MR valve usually goes for $300-450 price range.
3. If you don't want to spend money on an MR one, Forge sells a recirculating CBV that works a lot like the MR CBV. It's also a lot cheaper. Check the Forge website. There's also an install walkthroug on the EvoM Features's Project Evo page.
4. These links should help provide you with some information:
http://features.evolutionm.net/article/projectevo/22
http://www.forgemotorsport.com
http://features.evolutionm.net/article/machvcorner/29
Good luck, and feel free to post up if you have any questions.