First off, does anyone know if they are smog legal in CA? Would the CEL come on if I connected all 3 vac lines to it instead of to the N75 but still kept the N75 connected to the harness?(Complete bypass)

 

An MBC will have nothing to do with whether or not you pass smog. I've got mine plumbed in how you described and it works like gangbusters. No CEL. I just have the n75 zip-tied up under the inlet pipe.

Do you have a MAP sensor? Be careful if you start fiddling with a boost controller, its a really quick way to open a very nasty and expensive can of worms..

 

Looks like he has a 2000 A4 1.8t which does have a MAP sensor.

 

Ok, thanks. Yeah, I'm just trying to decide between getting a new N75 or MBC since MBC's are a lot cheaper and I have to do a smog check soon for my registration. My N75 failed and I'm getting erratic boost right now and when I accellerate too hard, the overboosting sometimes makes the EPC kick in.