When it comes to mods I think the first thing you need to figure out is what your main goal is, that will help people give you some advice and narrow down your choices.

For exhaust, are you going purely for sound? If so, I would recommend you goto a few BMW meets and hope that enough different guys show up with different exhausts so you can check them out first hand.

For a BOV, I would just say go with the company you like the most, its not really a serious mod, its fun, go for it, if you go with AA thats definitely a reputable company so good choice.

Dinan I imagine you are going with because of the warranty?

P.S. Dman jealousy can be a b*tch, you might want to consider getting some group therapy sessions.