I've been 'round the block for the past 2+ years studying the various German PBs and this is where I ended up:
http://f30.bimmerpost.com/forums/sho....php?t=1299267
Just check my posting history if you want to follow my thought process as I worked through the decision tree...
This is something I posted a few days ago about the new Dinan PB:
"At first, when I heard about this $249 deal from Dinan I kicked myself for paying around one grand for a bench tune (= ECU flash) up at Jarek's at JR Auto Performance in Oakville, Ontario. And then I thought to myself...sheeit, for $249 what are they going to get, a fuel rail booster? Yep, and that's what you get. And no engine warranty with Dinan to pay for BMW's salvage work in case there's an issue. (There's a reason that Dinan won't include their usual warranty on this little piggyback--yep, you guessed it!--because it's a fuel rail booster for $249!) A fuel rail booster is what it is, and the word "Dinan" doesn't make it magic. You'd best do your homework and make a rational decision before you get yourself some cheap power for your $50K car. Chances are that you'll be fine...chance being what it is, that is.
Yes, I paid another $750 for a custom tune, and I'm glad I did. The engine performance is just what I'd hoped it would be: Greatly decreased turbo lag, way more "take" down low, even and smooth acceleration all the way to the high end, much improved acceleration at the high end, and nary a hiccough along the way at any time.
Here's the story of my custom tune: http://f30.bimmerpost.com/forums/sho....php?t=1299267"