Don't worry about not running a EBC, just get a gate a few psi less than what you intend to run and then control the rest with a Turbotech $35 job. You will be surprised how well it works, I would run this if I didn't want switchable boost
Water cooling for the MVR, not running it... I don't see a need unless it's a full race car maybe. More of a gimmick
I use a 1bar spring and Profec B Spec II (only because I got it cheap second hand, I would rather a blitz dual solenoid)