I read the discussion from the thread below and found a water injection kit ($170) on ebay.
Does anyone has a similar system installed on your e34? Does it work? Technically, with this system, I should be able to use 87 octane gas on my 525i and save money from buying 91 gas.
http://www.bimmer.info/forum/showthread.php?t=23997
ebay
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