I gotta synchronic blow-off valve and in the instructions it mentions ensuring a proper tune is given after installation. What will the BOV change?! If you maintain the recirculated configuration, then no tune should be needed, correct?! I just need a sanity check before I install it...

http://jdmultimate.com/i-71925.aspx do I need need either the aluminum or stainless-steel weld-on flange for installation on the EVO-X?! If so, which one is recommended?? And does the "weld-on" denote that I gotta weld it myself??? This will be replacing (or does it just modify??) stock BOV...