If you're standing by the right front fender, looking at the engine, you should see
E7-E6-...E1 on the eeentake side
A7-A6-...A1 on the exhaust side

So all those letters should look just like that. E.g., the E7 is right side up when standing by the right (passenger side) front fender.

I don't know if it's critical, but do know that's how it came out and how I put it back. Photo confirmed just now.

Doing one at a time should be no problem, but if you're concerned and things are in a rotatable state, you can rotate the engine so one cap at a time can be removed when its cam lobes are facing up so there's no stress on the camshaft.

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2001 X5 3.0i, 203k miles, AT, owned since 2014