First off, very good review!! Really enjoyed reading about your changes and your perceptions after each change.
To add to this review, I just wanted to provide a little info from my experience. I have a 2010 328xi E90 with the BMW Performance Intake and Exhaust. Installed the PBX two days ago and the ECU has just about completed the handshake with the PBX in Map3. Word is it takes about 120 mls or so. YMMV. At this time I am really enjoying the no lag feel in the starting gears and the confidence to pass while in 5th and 6th. To back up the OP above, the sound of the exhaust is amazing once you blow/burn the packing out.
Everything the OP posted above is spot on. I am looking to talk with a shop in Northern MD this weekend that can dyno AWDs and getting some runs done so I can actually see what the final hp/tq output really is.
To the OP, grats on your changes and I'll be happy to back up any comments on the 328 side.
2010 E90 LCI/LeMans Blue
6MT with OEM SSK, Performance Intake and Exhaust
Oyster-Black Dakota Leather, M Sport Package w/NAV & Logic 7, 18" Series 193M Wheels & Xenon Headlights