I've noticed my engine idle drops substantially when I turn my wheels all the way (right or left). What's up? Is this normal? The drop is more than subtle, to the point where engine seems like its going to die, but then idle returns after a few seconds.
That's normal. If you hold you're wheel at full lock, the power steering unit tries to help you out, but obviously since your wheels are as far as they can go, it struggles and the engine speed drops slightly as the Power Steering uses more energy - It's not really noticable with bigger engines, but on the 316/318 its quite noticable.
Try this, let your car idle for a bit, and then put on your lights and your brights - the engine note should dip just a little. Or even better, when your car is idling and you switch on the air conditioner, the same thing happens - it is all the same principle.