Not sure about the cleaning up the intake, but many recommended oil change regularly.
Back to octane, IF you drive 128 as a normal car, you wouldn't notice any differences between AKI 87 or AKI 95. You can keep using 87. No problem.
IF you drive it on a race track, or drive like racing on the street, you may see some differences but not sure how much. You'll use a lot of gas anyways.
One of the reason I use Shell 91 is that it has no ethanol. I hate ethanol.