After installing a couple hose clamps, the issue seems to have disappeared. The checkengine light also went away after a ~15 minute drive (after restarting the car), idle is very smooth again even when pulling in the hoses that are now clamped up!

I could not find any sign of even the slighest bit of damage or cracks on either side of the hose, so I'm suspecting it really is just the missing clamps that was causing this problem.

Do you reckon it's still best to replace the hose, just in case?

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2002 BMW E53 4.6is - Estoril blue
1984 BMW E30 325 - Zinnoberrot
1964 Chevrolet Chevelle 300 - Meadow green