Did this fix (disconnecting DME from alternator) work? I am also at my wits end. I have spent a shit-load of $$ on my car only to have it break up when it down-shifts ant at high RPM. I'm about to get rid of the car it's so annoying, Thanks!
Found this group, and without stoking flames about turbo vs NA, I view the E90 330i as the best handling and competitive street car of the bunch, in an SCCA Street trim.
The lighter weight with same stock suspension fittings and componentry give the advantage right out of the box, based on its S package' front swaybar, car's lighter weight, + adding the monstrous 23.6mm rear bar from the E93 M convertible.