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      02-03-2014, 10:16 PM   #4
Carl Morris
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Drives: 2008 335xi 6MT
Join Date: Feb 2012
Location: San Jose, CA

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In my opinion 91 octane is not sufficient for the Aggressive tune. But I'm pickier than Cobb, I like almost no knock events ever. They tune for some, some of the time. With Aggressive on 91 if you datalog you'll probably see a lot of minor knock events. But of course the ECU handles them reasonably well, so it's up to you how much you want to "ride" the knock sensor. But there is a point of diminishing returns where more timing is being pulled than would have needed to have been with a more conservative tune.