At the age and that you've replaced the intake cam sensor I would replace the exhaust cam sensor but I don't suspect that as your problem.

The type of stumble you describe suggests DISA valve and very close to the mileage when mine went tits up.

I rebuilt mine with aluminum/titanium parts rather than replace with a new one that has the same plastic parts.

It's very Simple to pull the DISA valve and look at the flap.

I had to rebuild wifes as well but rather than spend $75 for the kit I spent $0 using nuts and a bolt I had laying around.

__________________
2011 E70 • N55 (me)
2012 E70 • N63 (wife)