I'm planning on getting a custom tune soon. What is recommended, a MBC or the Passive Boost Emulator?

 

Either will work. The Passive boost emulator is included with the flash, and it works very well, so the choice is up to you.

 

With the MBC you can change the boost when ever you want (if you were to put race gas in you could raise the boost). I'm pretty sure you have to send your ECU back to Vishnu to get the boost changed with the Passive Boost Emulator.