I too plan to do the same with the rings and that duck bill plastic thing. Just need to order and take a day off to remove it all and get the intake cleaned before reinstall.

But I did fit my idle. I crimped the tube to an almost closed position. I did so little by little. Was easy since all the rubber was new, so the idle control valve just came on and off without a fight. Eventually I got to an idle I liked. The tube is still open on mine, just not a whole lot.

The 560 is a bigger engine, so maybe it should be open. My understanding was that the tube was there to let some air through to prevent a full out stall incase the IAC reacts slowly.

Anyway, idle is at 800 now and everything seems ok. But I still have an irregular idle issues. Hence my wanting to replace the rubber under the intake next.

By the way, the vacuum trees to the injectors on mine were the worst. They had cracks all over!

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car