Hi, 2009 non-turbo. Replaced timing chain.
Idle hunts a bit, its not that bad but I don't think it was doing this before.
I did not remove the throttle body and thus did not replace tensioner. I only mention this because unlikely its a vacuum leak since I only removed the intake tube.

I think I read that the ECU may have to relearn the cam timing, is this true?

BTW, before the guide and chain replace there was a slight rattle at idle when in gear (auto) and its definitely gone now.
As far as the replacement itself, I found that a ratcheting closed end wrench was very useful for the upper friction wheel bolts. They were corroded a bit so I was unable to spin those by hand after loosening and i would have went mad doing it with a standard box end wrench. Perhaps low profile socket would work also. Other than that it was easier than I thought, about 8 hrs total. I did remove the radiator support, never done it before and it only took 10 mins so seems silly not to do that.

 

Any DTCs?

N12 engines don't product any noticeable engine vacuum at idle anyway due to the variable valve lift system. That's why there is a separate vacuum pump driven by the exhaust camshaft that supplies vacuum to the brake booster.

As for the relearn, yes, you should have reset your adaptations before you started the engine. Don't worry, that's not critical as the engine will eventually learn and adjust. Clearing the adaptations will start the process faster.

Why would you replace the timing chain and not replace the tensioner? You need to do that right away! Did you replace the guides? Sprockets? Hub seal?

 

Yes, used a timing kit with all the usual parts, new chain and crank sprocket.

I don't have the bentley manual thus I mostly used an online guide from a vendor (all the guides refer to turbo) and they did not have any detail on removing the tensioner bolt so I assume the tensioner bolt on the turbo is easily removed?
On the non turbo you have to remove the throttle body to get the tensioner bolt out and it wasn't clear to me if this is even possible with the engine in the car. Also did not have any TB gaskets and my local mini dealer parts dept is basically useless.

Anyhow tensioner is not really a wear item, right? I think only reason its included because it was revised.

Edit - I do have the Mini FSM and it says remove TB to access the tensioner but of course it does not say how to remove TB.