I just picked up a 2006 Z4 3.0si (Titanium silver, premium, xenon, heated seats, and sport) and this is my first BMW. I decided to switch from the dark side for a while. Any recommendations for must have mods?

Congrats on the purchase! As for mods, I'd just enjoy the car as it is for while, then decide what needs to be upgraded.

I'm sure others will chime in and give you some good recommendations.

Your car seems pretty well-optioned as is. The most commonly recommended mod is dropping the run-flat tires, but from reading posts by people with the facelifted models, it seems the suspension is better set-up for them than the original cars. Just enjoy your new ride.