You can also search www.car-part.com
or junkyards for a used manifold, and not spend $1k on it. I got mine for $225 shipped. If you look for used, you want a 330i or 330xi car made AFTER October 2005. This ensures you get an E90 part. Do not buy a 328 manifold, it won't help you.
You also don't need the manifold for the tune to make a difference. I bought the tune and got lucky with finding a manifold right afterwards. I applied the tune, and ended up waiting a few weeks to have time to install the manifold. Installing it yourself works too, it's a drop in replacement on the 325.
(Just, um, make sure all the hoses are FIRMLY connected. I ended up needing the dealer to troubleshoot it, since I knew I heard every hose click into place, but apparently they can click without being firmly seated. Good times.)